Extreme rich condition

[Perry Mitchell]

Before any work was done and before the plenum was removed, the motor ran extremely rich. After talking with Marc and Jerry, I removed the plenum and eliminated the complete secondary system. I replaced all the injectors with FIC ones and the fuel pressure regulator with Jerry's new and improved unit (which I have to say is a work of art). The prom was re-calibrated by Marc and a resistor was installed between pins B22 and C18 on the computer which got rid of the code 66 that I had. I now have NO codes but still have the extreme rich condition. I suspect a failed sensor or vacuum leak but with all the vacuum stuff removed and ports capped off, I am at a loss. Any ideas?

[-=Jeff=-]

How are you detecting the rich condition? Are you using a scan tool? if so, do you have logs?

[XfireZ51]

https://www.zr1.net/forum/showthread.php?t=25660&highlight=OBD1+codes

What's a code 66?

[Perry Mitchell]

A code 66 is a power fault for the valet switch.

[Perry Mitchell]

I do not have a scan tool but what I did was jump the terminals A and B in the ALDL connector and it showed no fault codes, only the code 12. All the plugs are black and sooty and the exhaust is very black and rich. I can't let it run very long as it smokes us out of the area.

[XfireZ51]

I do not have a scan tool but what I did was jump the terminals A and B in the ALDL connector and it showed no fault codes, only the code 12. All the plugs are black and sooty and the exhaust is very black and rich. I can't let it run very long as it smokes us out of the area.

Have u checked coolant temp sensor, not the gauge sensor?

Dynomite,

Need to add Code 66 to ur list of MALF in stickies.

[Perry Mitchell]

No, have not checked the coolant sensor. Can I do that without removing the plenum? It is rich right at startup.

[PhillipsLT5]

Were the FIC injectors new or rebuilt?

[Perry Mitchell]

Were the FIC injectors new or rebuilt?
I assume they were new as I bought them from Jerry and I am sure he would have told me otherwise.

[XfireZ51]

Also, have u looked at Fuel Pressure Regulator. Can u put an FP gauge on the right hand fuel rail?

[Bradjon]

I had something like this happen and it was a o 2 sensor wire had burned on the exhaust

[Perry Mitchell]

I have a fuel pressure gauge installed where the Schrader valve was. It reads about 45 psi which I think is a little low. It bleeds down slowly. How long should it take to bleed to zero?

[Paul Workman]

I had something like this happen and it was a o 2 sensor wire had burned on the exhaust

YES! (beat me toit!) A shorted O2 sensor will signal LEAN to which the ECM responds with increasing the injector dwell time, flooding that side with fuel.

In my case, the O2 voltage would intermittently short to ZERO, resulting in a lot of my hair pulled out before I bought a scanner and caught it in the act while driving. Making matters worse, the situation did not always throw a code. But, after smoking some time, I'd get an SES light. (This experience was on a 95 LT1 base car).

The question I have is, are the plugs on BOTH sides showing rich?

[Perry Mitchell]

I will pull the plugs this morning and inspect them. I am sure they need to be cleaned anyway. I suspect all cylinders to be rich. Don't the 02 sensors need to be heated up before they come into play. The sensor wires are definitely not burnt and the sensors are new but probably sooted up as well. I really appreciate the help.

[Perry Mitchell]

Just as I suspected, all 8 plugs were carboned up. Something is causing too much fuel to be introduced to the new FIC injectors. The FPR is also new and the prom properly calibrated. It has to be a malfunctioning sensor but I do not know how to test them. Maybe the MAP sensor?

[Paul Workman]

The fuel pressure (on mine) reads 45 psi after turning the intention switch to ON and the rail primes (normally). The pressure remains constant to within a pound (psi) over 30 minutes. If your pressure bleeds off by 3 or more or drops to zero in 30 minutes, it is an indication of a injector or check valve leaking.

If you tape the pressure gauge to the windshield and go for a drive, the pressure with light throttle should be ~45ish. But, at WOT, the pressure should jump to ~!53-55 psi range and hold there as long as at WOT.

Hope this helps...

P.

[Perry Mitchell]

Thanks Paul. This information gives me something to watch and tomorrow I will time the pressure drop on the gauge. Is there a check valve somewhere in the system other than the fuel pressure regulator? Maybe at the pump? However, I don't see how a pressure drop, when the key is off, has any effect on the rich condition I have.

[LGAFF]

How old is the gas? What is the gas color?

[Perry Mitchell]

How old is the gas? What is the gas color?
Thanks for the suggestion but the gas is fairly recent and is non-ethanol 87 octane which is the highest non E gas I can get in my area. Marc has compensated for that when he re-calibrated the prom.

[LGAFF]

I chased an issue after a car sat for the winter super rich fouled plugs, drained the tank it was yellow and once I swapped for fresh car ran fine...

[Perry Mitchell]

I will try fresh gas tomorrow but I don't understand how stale gas makes for a rich condition. I will report what I find. Thank you

[LGAFF]

Pics of gas, plugs after running just a few minutes, plug post flush

[Paul Workman]

Thanks Paul. This information gives me something to watch and tomorrow I will time the pressure drop on the gauge. Is there a check valve somewhere in the system other than the fuel pressure regulator? Maybe at the pump? However, I don't see how a pressure drop, when the key is off, has any effect on the rich condition I have.

My bad - my unspoken thought was to verify the fuel pressure regulator was not going haywire: I shoulda said that up front (and the rest would have made more sense!).

Clarification needed here: Yes, there is a check valve - one each in both pumps. But, you're correct in that a leak-down test (which I was describing) would not have anything to do with ALL of the cylinders running rich: more an "FYI" for future use perhaps.

[-=Jeff=-]

Thanks Paul. This information gives me something to watch and tomorrow I will time the pressure drop on the gauge. Is there a check valve somewhere in the system other than the fuel pressure regulator? Maybe at the pump? However, I don't see how a pressure drop, when the key is off, has any effect on the rich condition I have.
Fast bleed off of fuel pressure at key off could show signs of leaking injectors

[Perry Mitchell]

Fast bleed off of fuel pressure at key off could show signs of leaking injectors
True, however I had the problem with the original injectors. I replaced them with new FIC injectors and the problem continued. I am at a loss.

[-=Jeff=-]

True, however I had the problem with the original injectors. I replaced them with new FIC injectors and the problem continued. I am at a loss.

So I suggest, pulling plenum, pull injector rails, leaving everything on the rails. Put the rail over a cheap dollar store roasting pans, connect battery, turn key to on, look at injectors. See if any are dripping or leaking.

I bought rebuilt FIC injectors in 2008, I ended up having 2 leakers and no issues since. Still using same injectors.

This will confirm fuel not leaking.

I also think you need to get a scanner on the car while running and see what the data shows. If you don?t have a scanner maybe someone lives close, if you were near me I would be happy to help with my scanner

[Perry Mitchell]

Good advice Jeff. I will probably end up doing just that Wish you were closer to me.

[-=Jeff=-]

If you have an Android device.. you can get ALDLDroid for $20 and then buy a Bluetooth or usb cable and use the android. Or use a windows computer with TunerPro, which is also free.. having these cars especially at 30 years old these tools are helpful

[-=Jeff=-]

This cable and tunerpro on a windows pc would work

http://www.reddevilriver.com/site/mobile?url=http%3A%2F%2Fwww.reddevilriver.com%2Fal dl.html#2625

[Paul Workman]

This cable and tunerpro on a windows pc would work

http://www.reddevilriver.com/site/mobile?url=http%3A%2F%2Fwww.reddevilriver.com%2Fal dl.html#2625

DITTOS on a "scanner". Mine is "NLA", but it has paid for itself many times over in frustration alone! (Have wanted a "Notebook" and Tunerpro for some time. I have a birthday coming up...;))

[Hib Halverson]

You likely don't need to fuss with taping a pressure gauge to the windshield?at least not yet.

If you tested fuel pressure per the service manual and saw 45-psi peak after key off then the pressure drops. Your pressure is low. It should be 48-55 psi. If pressure drops after the pump shuts off you may have a leak.

A possible leak coupled with black sooty plugs tells me to investigate the possibility of a faulty FPR, faulty injectors, faulty ball check in the pump or anything else which can bleed off fuel pressure.

[-=Jeff=-]

You likely don't need to fuss with taping a pressure gauge to the windshield?at least not yet.

If you tested fuel pressure per the service manual and saw 45-psi peak after key off then the pressure drops. Your pressure is low?should be 48-55 psi?and you have a leak somewhere.

A possible leak coupled with black sooty plugs tells me to investigate the possibility of a faulty FPR, faulty injectors, faulty ball check in the pump or anything else which can bleed off fuel pressure.

Considering this is the same with the OEM and Jerry's FPR, I am guessing that probably is not the case, but still a possibility.

[Marc Haibeck]

Hi Perry,

The engine will run very rich at idle if the MAP sensor vacuum hose is not connected or leaking.

The manifold vacuum reported to the ECM should be 40 kpa at idle. Since you don't have a scanner measure the voltage between pins A and B on the MAP sensor. It should be 1.7 volts at 40 kpa. If the voltage is greater than 4 volts the ECM will command the injectors to run full rich at idle.

[Perry Mitchell]

Thanks Marc. I will check that out and report back.

[Perry Mitchell]

Hi Perry,

The engine will run very rich at idle if the MAP sensor vacuum hose is not connected or leaking.

The manifold vacuum reported to the ECM should be 40 kpa at idle. Since you don't have a scanner measure the voltage between pins A and B on the MAP sensor. It should be 1.7 volts at 40 kpa. If the voltage is greater than 4 volts the ECM will command the injectors to run full rich at idle.
Marc. I finally got the plenum back on and after startup, the car still runs very rich and idles rough. I connected my mutimeter to pins A (Black wire) and B (Green wire) and got a 1.0 volt reading. Does that indicate a bad MAP sensor?

[Marc Haibeck]

That's at good MAP sensor signal at idle. The sensor is requesting idle fueling.

How does the engine run when you drive the car? It should run smoothly when accelerating. Even if it is running rich the engine should run smoothly but might be down on power because there is too much fuel. I'm wondering if there is a misfire?

Are the spark plugs carboned from the old fuel injectors? You don't need to get a new set of plugs if they are just dirty. The tips can be cleaned by spraying them with carburetor cleaner, letting them dry. Then heating them with a Propane torch.

[Perry Mitchell]

I should remind you that this motor has been transplanted into a 67 Camaro, not that it should matter. The car isn't drivable yet as it is being readied for paint and reassembly. I cleaned the plugs with brake cleaner, which were very sooty but not hard carbon, prior to startup and after I installed new injectors and removal of the secondaries and the installation of your re-calibrated prom. The SES light is on steady with no flashing codes. I can't let it run more than a 30 seconds as it will choke me out.

[XfireZ51]

If the SES light is on steady, then its in Limp Home mode which would dictate it to run rich. And you say you have no codes altho the SES would indicate there is(are). How are you reading for codes?
I would follow Jeff s advice on getting a scan tool like ALDLdroid.

[-=Jeff=-]

Or jumper pins a&b on the diagnostic connector and read back the codes, each code is 2 digits repeated 3x first one is always 12, it would be flash....flash..flash (does represent time delay) the is would repeat.. after 3 each code will appear.

What year harness did you use?

[Perry Mitchell]

It's an after market harness for a 91 LT5 made by Ron Francis Wire Works. It seems to be very accurate when compared to the original harness I removed from the wrecked ZR1. I had a code 66 that I detected by jumping pins A and B in the ALDL connector but that went away after installing a resistor as you and Marc suggested. I have no codes now, other than code 12, as detected by jumping the ALDL pins with a paper clip. I do not have a scanner YET.

[Hib Halverson]

If the MIL is on but there no fault codes, then something is messed-up with the engine controls installation and, as this is an LT5 into 1G Camaro using an aftermarket harness, it might be difficult to solve this problem.

Is the calibration in the ECM also from a '91?

[Perry Mitchell]

Yes, the ECM and the recalibrated prom are from the wrecked 91 Z

[-=Jeff=-]

Yep Hib posted before me.. if no codes but an SES. You need to confirm ECM and PROM on someone?s 91z. Then if those work fine, look to the harness..

[Marc Haibeck]

It looks like everybody's ideas are heading in the same general direction. If the ECM blinks a code 12 it means that the ECM has passed the power up self test. That suggests a good ECM.

Is the chip adapter module plugged in 100% into the socket?

However like Dominic pointed out, if the engine is running and the SES is on with no error code set, the ECM may be running in limp home mode. In limp home mode the engine will run like you are describing, rough due to low spark advance and very very rich with fuel.

Like Jeff said, test the ECM in a ZR-1. You can install it in any model year ZR-1. You will get a SES and different error codes depending on the differences from '90 to '95. However, if the ECM is good the ZR-1 will idle smoothly and without excessive fumes.

[XfireZ51]

So just to summarize,

1. You have a 91 ZR aftermarket harness, no CCM
2. A stock C4 ZR ECM that flashes a code 12
3. A re-calibrated stock prom using a 91 Mask ID, or is it a recalibrated prom on a daughter board?
4. You have verified pinouts for ECM to aftermarket harness
5. An SES light that comes on immediately upon startup.

Am I missing anything?

[Perry Mitchell]

So just to summarize,

1. You have a 91 ZR aftermarket harness, no CCM
2. A stock C4 ZR ECM that flashes a code 12
3. A re-calibrated stock prom using a 91 Mask ID, or is it a recalibrated prom on a daughter board?
4. You have verified pinouts for ECM to aftermarket harness
5. An SES light that comes on immediately upon startup.

Am I missing anything?
That about sums it up. It has a stock re-calibrated prom, no daughter board.

[Perry Mitchell]

If the SES light is on steady, then its in Limp Home mode which would dictate it to run rich. And you say you have no codes altho the SES would indicate there is(are). How are you reading for codes?
I would follow Jeff s advice on getting a scan tool like ALDLdroid.First off, I would like to express my appreciation for all the help you guys are giving me. I
have ordered an ALDL to USB cable as Jeff suggested. I plan to use it with my laptop. Hope I can figure out how to use it. I also have another ECM that I bought years ago. It is a re-man from Delco without a prom. I will swap them out which should eliminate the need of finding another ZR1 owner in my area.

[XfireZ51]

The ECM isn?t reading the prom and so its in Limp Home Mode which uses a static fueling and spark map just to do what it says. If somebody nearby has a 91 prom, u could throw that in first and see what happens. It?ll probably start the motor, just not very drivable. If that happens then prom may be corrupted. My guess is that or wiring is suspect in that order.

[Perry Mitchell]

I just swapped out the ECM with the re-man unit that I have and found no difference. I am sure Marc checks out the prom during the re-calibration process. I will recheck my wiring AGAIN. I rechecked my SES again. With the ignition on the light is on steady. Turn ignition on, jump the A and B pins in the ALDL and the SES light blinks a 12 code. Start the motor with the ALDL pins jumped and the SES light blinks rapidly. Then I pulled the jumper off while engine is running and the light goes off. I hope that makes sense and that I'm not bothering you guys too much.

[-=Jeff=-]

I don?t feel you are bothering us. The symptoms are just odd.. that is all. Do you have wrong schematics with details you can share? It is hard to diagnose some things without info like that. How is the SES wired in the harness??

Calibration. Is probably fine. What are the numbers on the ECM, you say you have a remanufactured one.. from where? When did you get it? Let?s confirm the ECMs are correct

[XfireZ51]

When u turn ignition ON, do not start motor, does SES flash ONCE and then remain ON until motor is started? Or does it not FLASH and stay ON after motor start?

[A26B]

Do your ECM?s have a GM PN still?
Please post the numbers


Sent from my iPhone using ZR-1 Net Registry (http://r.tapatalk.com/byo?rid=90383)

[Perry Mitchell]

Hey Jerry. Back from vacation? The original ECM from the wrecked ZR does not have any numbers or sticker. The re-man ECM has a 16163993 on the box along with a DELCO sticker but no info on the ECM itself. Since both ECM's had the same effect, I am going to re-install the original ECM that ran the motor prior to the car being wrecked. I have been asked if the injectors you sell are new or reconditioned. I believe they are new, correct?

[Perry Mitchell]

[QUOTE=XfireZ51;311129]When u turn ignition ON, do not start motor, does SES flash ONCE and then remain ON until motor is started? Or does it not FLASH and stay ON after motor start?[/QUOTE

When I turn the ignition on, the SES light flashes once and then stays on. Then when I start the motor, the light goes dim, barely visible. I hadn't noticed that before, interesting.

[A26B]

Hey Jerry. Back from vacation? The original ECM from the wrecked ZR does not have any numbers or sticker. The re-man ECM has a 16163993 on the box along with a DELCO sticker but no info on the ECM itself. Since both ECM's had the same effect, I am going to re-install the original ECM that ran the motor prior to the car being wrecked. I have been asked if the injectors you sell are new or reconditioned. I believe they are new, correct?

Yes, they are new, flow-matched.

[XfireZ51]

3993 is a ZR ECM. Same as my ECM in 92.

[Marc Haibeck]

Just to be sure, I made a copy of your calibration and installed it on a '91 ZR-1. The engine idled smoothly with the normal low level of fumes for a cold engine. After two minutes the system went into closed loop at 118 degrees F. The car has catalysts. After two minutes there were no fumes at all.

Does your wiring harness have the Secondary Relay modules? I'm wondering if the fuel injectors are wired together. If so, there would be twice the fuel delivery than the engine needs at idle. Both injectors are driven when the throttle is opened .5% or more. Does the rich condition go away when the engine is idled at 1000 rpm?

Is your SES lamp an LED? If so it is normal for it to glow dimly when it should be off. A resistor needs to be added in series to reduce the drive current when a LED is used.

[Perry Mitchell]

Marc, I wasn't concerned with the work you did on my prom but thank you for confirming that. I am not familiar with the secondary relay modules. Where would I begin looking for them? I have never let the car run for 2 minutes to get warmed up. I will back the car out of the shop so it can run without smoking me out. The car does not have cats. My SES light is an LED so good to know that the dim condition is not a concern.

[-=Jeff=-]

Do you know how the injectors are wired in the harness?

Module looks like this:
http://www.whiteracingproducts.com/images/10086284.jpg

[Perry Mitchell]

I don't have anything that looks like that and the wire harness instructions doesn't make any mention of it. When I removed the harness from the wrecked ZR, I don't remember a sensor that looked like that. Where would it have been in a stock 91? What color would the wires/connector be? I still have the cut up original harness which I use for reference all the time. Each pair of wires for each injector were pre wired to the connectors. Each pair of wires were run to a panel that was supplied with the harness. The computer was prewired to this panel. The instructions told me which terminal on the panel to connect the injector wires to which indirectly connected them to the corresponding pin on the computer. Hope that makes sense.

[-=Jeff=-]

Sounds liek the injectors are not wired correctly, however it is concerning that you don't have a wiring diagram or pinout for the custom harness

[Perry Mitchell]

I'm not sure why you say you don't think they're wired correctly. Could you explain why you are concerned?

[-=Jeff=-]

Well, you don?t have the secondary injector modules so it sounds like the injectors are tied in pairs. Doing that will change the resistance of them. That also changes the load to the ECM . I was going to suggest disconnecting one injector at each cylinder and starting the car to see how it is.

Do you have a harness Pinout to show the connections from the ECM? Sounds like it is with the harness itself, but I am just guessing.

[Perry Mitchell]

But with the vacuum actuated secondaries removed and the prom re-calibrated for that condition, aren't both injectors working all the time, although equally, so no need for a secondary module? Where was the module located in a stock ZR? I know I'm being a bother but please don't give up on me.

[grahambehan]

Hi Perry. Ok so Mark already said that over 5% the secondary will turn on. So if you have the primary and secondary injectors wired to the same ground they will both fire up until that point, hence rich fuelling since when the ecm commands secondary function there is a multiplier of 0.51 to the pulse width. Im sure that if that if the wiring layout is explained to Mark he can send you a calibration that fixes the issue.

Graham

[Perry Mitchell]

Looks like I have some work to do!

[grahambehan]

Perry, not really its a simple fix once Mark is aware.

Graham

[Marc Haibeck]

I will modify your calibration so that it delivers 50% less fuel at idle.

We will see if the fuel injectors can deliver such a short pulse. Like Jeff pointed out the ECM will be driving twice the normal load with two injectors in parallel. It's already doing that so we are off to a good start.

[XfireZ51]

I will modify your calibration so that it delivers 50% less fuel at idle.

We will see if the fuel injectors can deliver such a short pulse. Like Jeff pointed out the ECM will be driving twice the normal load with two injectors in parallel.

Good question Marc. Will the ECM be capable of sustainably driving 16 injectors without blowing a fuse? Apparently doing that at idle now.

:happy1::happy1:

[-=Jeff=-]

But with the vacuum actuated secondaries removed and the prom re-calibrated for that condition, aren't both injectors working all the time, although equally, so no need for a secondary module? Where was the module located in a stock ZR? I know I'm being a bother but please don't give up on me.

Secondary modules balance the injector load placed on the ECM. Example.. typical injector is ~16-18Ohms.. The ECM is set up to drive that 16-18 Ohms, with some room for error..

Now, I have 2 injectors @ 16 ohm in parallel to the ECM, I am now at a total load of 8 ohms, which will require the ECM to drive harder, more heat and potentially premature failure..

The secondary module compensates for this, the ECM still sees the 16 ohm load but I can run 2 injectors. When the ECM is told to run Full power (above idle) the Secondary module receives a signal (like a switch) to power the added injectors.

Now if you ran a higher impedance injector (like ~40Ohms) then you are fine to pair them as the ECM sees the ~16-18 load..

As for location , the modules were located near the battery either on the firewall or just in front of the battery on the wheel well

[Perry Mitchell]

Time for an update. Because the consensus is that I have tied the injectors to the ECM in pairs since I do not have the secondary relay modules, Marc has provided me with another re-calibrated prom that reduces the fuel flow by 50% at idle. I cleaned the AIT sensor and the IAC sensor. I adjusted the TPS to .55 volts. The engine started and idled as before but this time I had no obvious rich condition at idle. But when the engine ran for 2 minutes, the rich condition seemed to re-appear. I am getting close but not there yet. I purchased an ALDL to USB cable and am trying to figure out the Tuner Pro application. I will let you know what I find out. Thanks Marc.

[-=Jeff=-]

Alright.. so the theory was right on the fuel. I have to wonder if the paired injectors are causing more load on the ECM. Based on you description, I wonder if it is going to closed loop after 2 minutes and the fuel tables might be off due to the way you have the injectors.

If you need help with TunerPro, I use it all the time and I helped create some of the ADX files

[Perry Mitchell]

My brother and I were trying to download the application on my laptop but were having trouble with it. He took the CD and cable with him to work on it this week. He is much more tech savvy than me so I know we will have a working solution next week when he returns. I also wondered if the computer went in to closed loop as well.

[-=Jeff=-]

Cool..

I have a nice ADX setup with a dash board for TunerPro.

[XfireZ51]

My brother and I were trying to download the application on my laptop but were having trouble with it. He took the CD and cable with him to work on it this week. He is much more tech savvy than me so I know we will have a working solution next week when he returns. I also wondered if the computer went in to closed loop as well.

Depend on what coolant temp was when engine was started. If CTS is >20C and <70C, C/L happens in 150seconds.
I agree w Jeff that the ?paired? injectors very likely would put a load on the ECM that I wouldn?t be comfortable w for the long term. Its the reason why the secondaries use the secondary relays to drive the injectors, altho they get their pulse width command from the primary.
One possible reason ur still getting rich condition even after cutting the idle fuel by 50% is because as the secondary injector gets it PW command from the primary, the ECM is still calculating the PW based in part on the Injector Bias. The IB the amount of time the ECM calcs in the PW for the injector to open. In a stock calibration that IB will be 579usec for the stock injectors. Plus there?s an additional 45-76usec for small PW (as in idle operation) since the stock injectors were not linear. This is assuming that the ECM is seeing 14.4 Batt voltage. If its less the IB is larger. Your use of FIC injectors also adds to the error in PW calc.
In your case, the ECM adds that IB to the calc?d PW, but it is doubled by the fact that the secondary injector is also firing. And the calibration doesn?t allow for you to modify the IB just for idle conditions. You could scale the IB back, but then it would be incorrect for all other engine operating conditions aside from idle.
Idle won?t be the only area affected. It will be rich also on decel w TPS at 0% and DFCO disabled.

[Marc Haibeck]

Perry,

Based on your observations, we may need to remove more fuel. We need to proceed carefully because if we remove too much it could lead to stalling which is a worse problem. A cold engine will tolerate a rich mixture because it needs more fuel. As the engine warms it needs less fuel so a rich condition can get worse as the engine warms. Since you are close to having scan data we should wait until you can observe the BLM and Integrator fuel trim values. Also report the TPS%. And the Port Throttle status, Open verses Closed.

In the meantime take a look at the oxygen sensor wiring. Make sure that there is a connector a few inches away from the sensor. The wires should not be hardwired and taped. The connectors should not have tape on them either. The sensor gets reference oxygen through the wires.

[Perry Mitchell]

You guys are talking way over my head now. What do BLM, IB and DFCO stand for. I hope my brother can understand your lingo. I know, with the help from you guys, we will get this figured out. Marc, the O2 sensors have a pigtail with a connector that is about 8'' long. They have a covering on some of it that is loose but then so did the original sensors.

[XfireZ51]

IB Injector Bias. Injectors have an opening and closing lag which must be accounted for when calculating Pulse width. Think of it the same way you think of Spark Advance. If the the Pulse Width is calculated as X, then the ECM must take into account how long it takes the injector to open in order to meter the fuel properly. The amount of time that it takes for the injector opening is dependent on the voltage available at the injector. The higher the voltage, the faster it opens. Its also a static number. Therefore, it is a significant fraction of the calculated PW when the PW is small, ie as in idle and decel operation.
Different injectors have different Injector Bias depending on their electrical properties.

DFCO- Decel Fuel CutOff - during deceleration w closed throttle, fuel is cutoff for emissions purposes. If this is disabled, then fuel will continue albeit at very small PW. In your case both injectors will continue firing.

BLM Block Learn Multiple. Used by ECM to adjust fueling when in Closed Loop.

[Perry Mitchell]

Thank you Dominic. I never would have figured those abbreviations out . I asked Siri what BLM stood for and all she said was Black Lives Matter which is fine but not what I was looking for.

[Marc Haibeck]

Perry,

The data items that I requested will be easy to find once you get the scanner working. The names will be on a list that is filled in with data from the engine.

You can you can write the numbers down and report them here. Or if you have the time you can learn how to record them on a graph and post the graph here.

From your description it seems like your oxygen sensor cables are okay.

[Perry Mitchell]

We spent A short time with the Tuner Pro scanner. We have a lot to learn with it. Do you see anything that jumps out at you other than the battery voltage. I am charging the battery now and will attempt another scan tomorrow.

[Perry Mitchell]

Wow, what lousy pictures I?ve posted. I can?t even read them myself. I?ll try again tomorrow

[-=Jeff=-]

What ADX file
Are you using? Where did you get it from?

[Marc Haibeck]

The data has a lot of logical conflicts. The ones that are the most notable to me are that the right oxygen sensor is at 0 mv. and the system is in closed loop mode. Normally the system will not go into closed loop if an oxygen sensor is not transitioning. This suggests that the wrong data is being listed for one of these PIDs.

The calibration is based on an 8EA configuration file. The scanner is showing an 8E ADX file. Try running the scan with an 8EA file.

[Perry Mitchell]

Let's see if I can explain this intelligently. The file we were using was 8E.adx and it was from a list that the website offered. It states it is for a 90 LT5 but they didn't list one specifically for a 91. All they listed was a 90 or 93 to 95. When my brother and I get together again, we will search for a 8EA adx. Does that makes sense?

[-=Jeff=-]

I have all of them. I put them together as the one you got while it works for you since you don't have a CCM. Mine I know will work correctly. What year do you need? 1991. PM me your email and I can send it to you

[-=Jeff=-]

Guys whether it is $8E or $8EA it will use the SAME adx as the output info from the ECM stream is the same..

HOWEVER.. Perry says he has a 1991, if it is wired for the a 1991 it should be $AF or $AFA and he could yuse the 8E.adx and most of it will work, but I sent him the one I made for the 1991 and should work for everything..

[Marc Haibeck]

I misspoke. His calibration is of course, a '91. It uses the AFA definition file.

[-=Jeff=-]

I misspoke. His calibration is of course, a '91. It uses the AFA definition file.

Marc thanks for the clarification. I have sent him the 1991 ADX.

[Perry Mitchell]

Using the file that Jeff provided, we were able to run some more tests. Here are the results. I don't know why the right O2 sensor doesn't register anything. The engine runs smooth in open loop but not in closed loop. No smoke in open loop but starts smoking when in closed loop. Sorry about the sideways pictures.

[-=Jeff=-]

There is something going on with the o2 if it is not changing from 0.. could be anything.. this is where the harness wiring diagram becomes very useful

[Perry Mitchell]

I agree. I will follow the O2 sensor wires back to the computer and see which pins they are connected to.

[grahambehan]

In your first frame with the engine not running, both sensors are reporting around 450 mv, so the heaters are working and the sensor circuit is reporting at that time. I would suggest swapping the sensors from side to side and see if it follows the sensor or stays on the right.

Graham

[tpepmeie]

Graham, from what I recall, the calibration sets the initial startup value to .450 volts. This happens in the initialization routine. Once the engine starts the sensor reports back the actual voltage.


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[Perry Mitchell]

I believe I have found the problem with the right hand O2 sensor. I got my original Bosch sensors from the wrecked ZR out of storage and compared them with the ones in the car now. The three wires on the Bosch sensors had the black wire connected to the weatherpak connector at the C location. My right side sensor was wired the same as the Bosch sensor BUT the left hand sensor had the black wire at the A terminal. If anyone can confirm this with their originals, I would appreciate it. Thank you

[grahambehan]

Graham, from what I recall, the calibration sets the initial startup value to .450 volts. This happens in the initialization routine. Once the engine starts the sensor reports back the actual voltage.


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Todd, thats interesting, I'll have to check that.

Thanks
Graham

[tpepmeie]

Todd, thats interesting, I'll have to check that.

Thanks
Graham

Had to dig out my source code to make sure I was remembering correctly.
In the calibration data, there is a value called "KO2FFO" which is the initial filtered O2 value when not running. In all the stock calibrations that value is .450v.

In the program, the O2 initialization routine starts at around address B26C, in the 91MY calibration. At first power-up, The program calls that calibration value and stores it in all of the various O2 RAM addresses. By the way, it does the same initialization for most of the key engine sensors (MAP, TPS, etc.).

To the OP, sorry for the hijack. I'll get back to lurking. Hope you get it sorted out.

[XfireZ51]

So Todd, are u saying that the sensor values we read at initial Power Up, not engine start, may not be the actual values for the sensors at that moment, ie TPS?

Also, how is the motor going Closed Loop w no X-counts coming from the right side?

[tpepmeie]

So Todd, are u saying that the sensor values we read at initial Power Up, not engine start, may not be the actual values for the sensors at that moment, ie TPS?

Also, how is the motor going Closed Loop w no X-counts coming from the right side?

re: the first question. not necessarily. what I described was the initialization at first power up, literally some of the very first sections of the program. After that, the various values get updated at specific intervals (milliseconds) based on sensor readiness checks and current values. Also, there are some variables which are stored in non-volatile memory even when the ignition key is off. That's the purpose of the "keep-alive" power (orange wire).

My supposition is that what we see in his datalog is the initialization value prior to startup, then replaced with the sensor reading after a certain amount of cycles have passed.

[Perry Mitchell]

Had to dig out my source code to make sure I was remembering correctly.
In the calibration data, there is a value called "KO2FFO" which is the initial filtered O2 value when not running. In all the stock calibrations that value is .450v.

In the program, the O2 initialization routine starts at around address B26C, in the 91MY calibration. At first power-up, The program calls that calibration value and stores it in all of the various O2 RAM addresses. By the way, it does the same initialization for most of the key engine sensors (MAP, TPS, etc.).

To the OP, sorry for the hijack. I'll get back to lurking. Hope you get it sorted out.
Todd, you didn't hijack. You just added some good usable information. I was wondering why the right sensor showed a value then disappeared.


I misspoke when describing the pigtails from the sensors. The left sensor was the same as the factory unit but the right sensor was wired wrong at the connector. I haven't run a new scan yet but I'm sure the sensor wiring was the issue with the sensor not showing a value.

[Perry Mitchell]

So Todd, are u saying that the sensor values we read at initial Power Up, not engine start, may not be the actual values for the sensors at that moment, ie TPS?

Also, how is the motor going Closed Loop w no X-counts coming from the right side?
Did you ever get a response regarding the motor going closed loop without a proper signal from the O2 sensors?

[Marc Haibeck]

Hi Perry,

I presume that the scanned data from the right oxygen sensor still shows zero volts.

Perform this simple test to verify that the wiring is correct. Back-probe pin C15 on the ECM and connect a volt meter. Ground the meter on the negative battery terminal. Turn on the ignition without starting the engine. With a battery voltage of about 12.5 volts, the voltage on pin C15 should be in the 350 to 425 mv. range. After about 60 seconds the sensor will warm up and start reporting oxygen. The voltage should go down to about 90 mv. after about three minutes.

The left sensor on pin A16 should do the same thing.

[Perry Mitchell]

Thanks Marc. I will do that test today and report back.

[XfireZ51]

Did you ever get a response regarding the motor going closed loop without a proper signal from the O2 sensors?

I did get a response from one of the tuning gurus on Third Gen.


I think that it can. The ECM usually just looks at the O2 sensor voltage for closed loop determination. That is either lower then a set value (200 mV) or higher then a set value (700 mV).

Because until in closed loop with prop gains there may not be x-counts.?

I have had instances where one of the O2 sensors would report a string of 0 volt readings, ie during cruise, and would still stay in Closed Loop. However, it could exit Learn mode after a certain period of time.
One of the reasons I switched from Bosch sensors. I don?t have that issue w the AC sensors.

[Perry Mitchell]

Marc. I did what you said and here are the results. I connected to the purple wire at pin C18 on the green connector and got .550v which declined rapidly to .160v in 1 minute. Then it slowly decreased to .084v in 3 minutes. Then I connected to pin A16 in the gray connector for the left sensor and got .570v which dropped to .160 in 1 minute and settled at .074 in 3 minutes. There was some variation in these numbers each time I did the test. Do they sound about right?

[Marc Haibeck]

Your test results show that the sensors are wired correctly and that the sensors are reporting reasonable oxygen levels.

Let's put the odd right oxygen sensor voltage scan data aside for now.

Image 257 shows the engine in closed loop, running rough evidenced by the 50 kpa manifold vacuum and running very rich on the right bank.
Left BLM125 + INT96/256 = .86 or -14% fuel trim.
Right BLM133 + INT192/256 = 1.27 or +27% fuel trim.
You are observing excess fuel in the exhaust which is consistent with the system adding a huge amount of fuel on the right bank.

Image 258 shows the engine in open loop with normal 42 kpa manifold vacuum. The fuel trim looks reasonable.
Left BLM120 + INT128/256 = .97 or -3% fuel trim.
Right BLM140 + INT128/256 = 1.05 or +5% fuel trim.
You are observing that the engine runs okay with no smoke in open loop.

I wonder if the ECM is malfunctioning due to noisy power? You should followup on the low system voltage reported in the scan data in post #81. The PID shows 10.7 volts. I suggest getting the system voltage to better than 12 volts with the engine running.

Check the following:
- The ECM grounds on pins B6, B17 and C12 should run directly to the engine block. They need to be direct runs with nothing else connected to share a ground on those wires.
- The ECM battery feed pin B11 should be a direct run to the battery positive terminal. Nothing else should be connected to it. It should not go to a terminal block and then to the battery. The wire should be 14 gage if less than three feet long. 10 gage if up to 10 feet long.
- The battery should be fully charged. You should not be jump starting the engine due to a discharged battery.

[Perry Mitchell]

Hello Marc
A lot of information there. Thanks for taking the time to post it for me. Did you read the post where I stated that the right O2 sensor that I purchased had the pigtail wiring incorrect? The black wire was in the wrong location in the connector. I have not performed another scan since I corrected their mistake but was corrected prior to performing the O2 sensor tests that you provided. I hope to do another scan today.

As far as the low battery voltage is concerned, I need to figure out why the alternator is not charging. It could be the way it is wired to the trunk mounted battery or the way it was reassembled after being apart for polishing. Shouldn't be to difficult to correct. I have always kept the battery charged and never had to jump start the car. I was surprised to see the low voltage when we performed the scan. That is when I discovered the problem.

My chores today are to follow up on your ECM wiring requirements. I really appreciate your and others help with my problems.

[Perry Mitchell]

I want to resurrect this topic as I think I?ve got things sorted out and would like the opinion of the members who gave me so much information in the past. I had to replace my alternator because the existing one seemed to have failed. I also managed to get the cooling system completely filled by using a vacuum system to get the water pump completely filled. I have attached pictures of my existing tune and would like your input. The engine starts very well and now seems to idle very well in both open and closed loop. The exhaust seems to have only minimal smoke. I think I got it. What do you guys think?

[-=Jeff=-]

Glancing at the BLM it is 115, you want it close to 128. 115 is rich and the ECM is pulling fuel

[Perry Mitchell]

Glancing at the BLM it is 115, you want it close to 128. 115 is rich and the ECM is pulling fuel

Oh great. How do I fix that?

[-=Jeff=-]

Tuning, however for now it looks much better than before.. the tuning the hone in on 128 should be when the car is driving on the road

[Perry Mitchell]

I just watched the entire data log which the previous still pictures were from. The BLM's, both left and right, started out as a constant 128 but half way through the test, they jumped down to a constant 115. The entire log was performed in closed loop. What's up with that? What is the correlation between the BLM and the integrator?

[-=Jeff=-]

integrator is short term fuel.. BLM is long term. when you start the car I will be in open loop for a set time, based on O2, running time and Coolant temp. so during this time BLM is locked @ 128. after that is goes to adjusting.. 115 is rich, but OK until you can get the car to a driving state and get some data while driving. I believe your tune is from Marc, talk him about what he would like in order to get the BLMs closer to 128..