Bogs for a second and then takes off

[StickWalker]

First off, I replaced the injectors with new FIC injectors and pinned the secondaries open with Hiabecks chip for 2ndy deletion. I did this swap around 500 miles or so ago and also changed the fuel filter at the same time.

Now the issue starts after a few minutes of driving before that it runs great. (Never has an issue from a stop) When the issue occurs I am in a gear coasting (foot off the gas) at around 2-4000 rpm, and when I hit the gas pedal it bogs down for a second or so and then takes off and pulls to 7000 no problem. It only ocurrs after a moment of high vacuum once its warm. I have replaced the MAP sensor and hose with no change, drove around with a fuel pressure gauge on the windshield which shows around 41 psi with the foot off the gas, and goes up to 51 when I press on the gas.


I've checked for vacuum leaks and cant find any. The only thing I have noticed is that #4 cylinder plug seems like it's running rich, Ohm's 16 when cold, havent checked when hot.

If anyone has any other ideas without just throwing parts at I would appreciate it.

Thanks,
Don

[Roadster]

IMO, it may depend on what gear you are in at the time you hit the gas pedal, and the speed that you are traveling. When I first got my Z 6 months ago, I noticed a similar situation, but found out that if you drop a gear or two and bring up the r's, no problem. I thought that at any gear with the LT5 it would be instant, and again depends on your speed and what gear you are in.

I don't think that one plug even if running rich would cause that situation, IMO, it would have to be loaded and fouled out for you to feel anything.

Just had ours out today, always a great ride.....have fun.....:)

[XfireZ51]

Did this happen before the 2ndaries were deleted?

[StickWalker]

Dom, this didnt happen before the secondaries were deleted, and there is not bogging for 5 minutes or so after starting it. Then ,only after coasting with the foot off the gas and like your slowing down for a light and then you get back on it, it falls on its face for a second and then takes off like it never happened.

Don

[We Gone]

I'm sure the secondary injectors are not on in the first 5 min. after start up as the temps have to be up before they will go active. This may be why you don't have an issue in the first 5 min. or with no secondary's are the injectors all working from start-up?

[StickWalker]

Steve, I believe the secondaries are all on all the time with the deletion chip. Plus this didnt happen for the first 3-500 miles after I deleted them. After searching some older threads I'm wondering whether an O2 sensor has died since the car has 100K miles on it.

Don

[We Gone]

Ok, was not sure what went into the prom after reprogram, If you can get a scanner to look at your 02's would help alot. I had a small hesitation when cold checked with scanner and found my right 02 was not cross-counting correctly numbers were all over, replaced both and it runs much better.

[XfireZ51]

The secondaries are active after 20C. At closed throttle, only the primary injectors are firing, however once TPS% is over ~ 1.2%, secondary injectors come on. However, the stock calibration has a delay for allowing the secondary plates to open. That's not necessary with secondaries disabled. When you close the throttle, you could be going into DFCO (Decel Fuel Cutoff). Did Marc disable this? With high vacuum of closed throttle, fuel is sucked out. You need some extra pump shot (AE) to make up for that fuel once you step on the accelerator.
Have Marc review your calibration.

[BennieC.]

My customer's car is doing the exact same thing as well. Marc also did the chip for the secondary elimination. I'm going to check it this weekend and try to find out exactly why it's doing it.

[StickWalker]

Bennie, I have been driving the car and it still does it but not as bad when first noticed. I really dont notice it when I am doing any spirited driving. It just happens like I said when decellerating/coasting and then hitting the gas. If I keep my foot just on the gas pedal its doesnt happen at all. So it just seems to act like it runs just a bit lean when coasting and jumping back on the the throttle.
My wife and I took it to the beach for the weekend a couple weeks ago and ran great. Good Luck

Don

[Paul Workman]

:happy1:

Well, kinda piling on, but mine too sometimes cuts out on hard decel when getting back on the throttle. I'd like to hear what Marc says about it, as I too have the same issue with the secondary delete - have had for 6 years now. It can be aggravating, but only happens on hard decel after running for "a while" in spirited driving conditions.

It isn't a big deal as it doesn't crop up all the time. But, I'd like to get to the bottom of it one day.

[Dynomite]

I have a 91' with secondaries eliminated and RC Injectors.

Three 90's all with RC injectors and secondaries including starter reconditioned like new.

All four ZR-1s have Haibeck chips.
All four have TB coolant blocked at Injector Housings.
All four have the Starter Relay installed.
All four have Jerry's gaskets and SS bolts.
All four have full compliment of Carter Bling ;)

All four accelerate like greased lightning with NO bogging or hesitation in any gear at all RPMs :D

Oh.........And a 90' (L98) with Haibeck Chip......also greased lightning :D

[WVZR-1]

All four accelerate like grease lightening with NO bogging or hesitation in any gear at all RPMs :D

Oh.........And a 90' (L98) with Haibeck Chip......also grease lightening :D

Just what is "grease lightening"?

I've seen "GREASED LIGHTNING" used in reference to maybe fast or speedy BUT "LIGHTENING" confuses me.

[Dynomite]

Just what is "grease lightening"?

I've seen "GREASED LIGHTNING" used in reference to maybe fast or speedy BUT "LIGHTENING" confuses me.

:sign10: I am a poor speller :D

Just got done making a set of New Oil Cooler SS Braided Hoses with Aeroquip re-usable fittings for a 90' ZR-1 and they fit perfectly first try.
I cannot spell "Aeroquip re-usable" sometimes but the hoses are perfect :D

I will take a photo tomorrow after I degrease (here I go again ;)) the little bit of oil spilled while doing the change over to SS Braided hoses.

I will try some runs tomorrow also to see if I can get it to bog or hesitate at all.

[WVZR-1]

:sign10: I am a poor speller :D



LOL - me too I believe

[Bearly Flying]

I have the same problem as the OP, ported plenum and IH's, secondary delete.

The car runs very well except for when it is in low throttle positions. ie normal traffic stop and go conditions.

Any periods of light or no throttle positions seem to generate a rich condition and flood the motor.
A decisive hit on the throttle will clear it's throat and all is good until the next lite throttle event.

It's not all that fun when you are in stop and go traffic.

I believe we are flooding the motor at low throttle positions.

[BennieC.]

It appears that Z owners that is having the problem have in commons are: 1) the secondaries eliminated
2) Haibeck chip

How about the injectors. What injectors do you have currently installed. I have talked to Marc in regards to this concern and he has 2 1990 that are doing the same thing as well. He suspecting injectors. I'm going to data log and check the car out this weekend. Will let you know what I find out. We can make some changes to the fuel trim if need be.

[Bearly Flying]

I have FIC injectors from Jerry.

Headers and a 3" exhaust, Ported plenum and IH;s, port matched heads. If that helps....

[Marc Haibeck]

Hi Bennie,

I resolved the problem that I was having with the car that was bogging or stumbling under light loads.

This is what I was seeing in the scan data. When the engine would bog the short term fuel trim would go down to about 90. As if the the fueling was really rich. Then the oxygen sensor voltage would then go to less than 50 mv. This would close the fuel injector and I would see 17 to 20:1 AFR on my wideband oxygen sensor.

If the calibration was set to open loop the car would drive perfectly so the fuel table was correct. I eliminated the problem by replacing the oxygen sensors. New sensors respond quickly to fueling anomalies and don't get stuck down at less than 50 mv when responding to a rich AFR.

[XfireZ51]

Marc,

You may recall I was chasing an issue w my O2 sensors earlier this year. Particularly the pass. side. On a scan, I would see a string of 0's for the voltage, which thee ECM would interpret as running lean. If that condition remained long enough, it would throw the LEARN function OFF and default back into Open Loop.
W a bit of accelerator, things would come back. You wouldn't feel any difference as it did that, but for purposes of tuning it would throw things off.
Some other tuners I communicated with suggested that AC O2 sensors were more consistent than the Bosch so I got two of them off Amazon. Voila!
No zeros, no open/closed loop flipping, no going into and out of learn.
However, I can't say that I experienced the bog others are sensing. I do see that on closed throttle decel, my WB will sometimes spike to 17 or 18:1 AFR.
I wonder if that's not the injector shutting down due to a too small pulse width being commanded, which brings up the issue of the injector offset. Another tuner using the ACCELs in a different motor saw the same thing happening

[Marc Haibeck]

Dominic,

I installed Bosch 13077 (similar to the OE sensor) and then the oxygen sensor performance was excellent. They solved the bogging problem.

In general, I think that the control system is not very good at fuel corrections that are greater than -10%. Then maybe it overshoots the adjustment and goes too lean. In the future when encountering the lean out problem, I'm going to adjust the AFR into the 13.2 to 16.1 range with my wideband and with the system in open loop. Then go to closed loop and make fine adjustments.

I have seen the deceleration trims in the 90's on some cars. I too think that it could be a fuel injector low flow limitation. Excellent oxygen sensors will help there too.

[XfireZ51]

Marc,

Interesting observations. Let me suggest you try the AC O2 sensor at some point. My experience and that of some others suggests it's more consistent and reliable. I have used the Bosch for a long time but more recently have found that for some reason performance deteriorates over time.
I wonder if the use of headers, creating a longer travel path for the exhaust, affects the accuracy of the Bosch.

Some questions:

1. Has your experience been w both exhaust setups or just the stock manifolds?
2.Is it coincidence that the "defective" sensor seems to be the one I have a harness extension on?
3.O2 voltage is small and the extra resistance doesn't work well w the signal from the Bosch??
4. If you still have the logs of those scans, what is the PW when you see the AFR spiking lean?
I'm assuming you're zeroing out the secondary injector delay on your secondary delete calibration.

[WVZR-1]

2.Is it coincidence that the "defective" sensor seems to be the one I have a harness extension on?


It very well might not be a coincidence. I'd think the quality of the components quite important. How long is the extension?

[XfireZ51]

It very well might not be a coincidence. I'd think the quality of the components quite important. How long is the extension?

I use the wiring and connectors from used O2 sensors so my extension adds about 9" in length. Just thinking out loud if there is any correlation to which side of the motor the defective sensor is usually found. Also, if it happens w motors using headers (the reason for the extension) as opposed to stock manifold motors.
Given the very low signal strength used for the O2 sensor, perhaps the Bosch O2 is marginal in those situations. Or perhaps it works fine at first but then deteriorates over time.
The O2 sensor I am now using is the AC AFS-74. It looks more like a Denso sensor than the Bosch. When I logged the ACs v the Bosch , the ACs seemed to tell a bit of a different story re: BLMs. Motor appeared to be running leaner than I had observed before. Another observation is that the motor does not drop in and out of C/L. Once there, it stayed in C/L.

[Marc Haibeck]

Dominic,
Your question 1. I find that oxygen sensor performance is better on OE manifolds. The OE manifolds are designed to jet each of the four cylinders across the sensor. With headers usually only two cylinders are in the sensors path.
Q 2 and 3. Extending the oxygen sensor cable has no effect on the sensors voltage to the ECM. Voltage drop is determined by resistance x current. Ohm's law. The sensors's current is so low that if the cable was lengthened by three feet the voltage drop would only be a millivolt or two. An insignificant loss. Adding tape or sealer to an extension cable can cause problems. The sensor gets its reference air through the connectors. Only use crimp connectors.
Q 4. I have a nice scan of the fueling going falsely rich on deceleration. At 2300 rpm the throttle was closed. The FI pulse width is 3.2 ms, then the sensor goes to 898 mv, very rich. The sensor stays at about 880 mv for two seconds. Meanwhile, the FI pulse is ramping down to 2.0 ms. Then the sensor snaps quickly to lean. About one second later everything is normal with a FI pulse os 3.2 ms. The new sensor switches faster from rich to lean, without running down the FI pulse to the point to where the engine misfires.
I always set the secondary throttle opening delay to zero, even though it doesn't matter if the secondary throttles are not present. The delay is for the opening of the ports, not the fuel.

[Paul Workman]

Dominic,
Your question 1. I find that oxygen sensor performance is better on OE manifolds. The OE manifolds are designed to jet each of the four cylinders across the sensor. With headers usually only two cylinders are in the sensors path.
Q 2 and 3. Extending the oxygen sensor cable has no effect on the sensors voltage to the ECM. Voltage drop is determined by resistance x current. Ohm's law. The sensors's current is so low that if the cable was lengthened by three feet the voltage drop would only be a millivolt or two. An insignificant loss. Adding tape or sealer to an extension cable can cause problems. The sensor gets its reference air through the connectors. Only use crimp connectors.
Q 4. I have a nice scan of the fueling going falsely rich on deceleration. At 2300 rpm the throttle was closed. The FI pulse width is 3.2 ms, then the sensor goes to 898 mv, very rich. The sensor stays at about 880 mv for two seconds. Meanwhile, the FI pulse is ramping down to 2.0 ms. Then the sensor snaps quickly to lean. About one second later everything is normal with a FI pulse os 3.2 ms. The new sensor switches faster from rich to lean, without running down the FI pulse to the point to where the engine misfires.
I always set the secondary throttle opening delay to zero, even though it doesn't matter if the secondary throttles are not present. The delay is for the opening of the ports, not the fuel.

I was unaware of the sensor sampling the air via the leads (i.e., though the wires) too. But, I can testify to the fact the sensor depends on the air it gets through the port where the wires enter the sensor.

After replacing one of my O2s, Just to add some reliability for "good measure", I sealed the sensor where the wires enter the sensor. I packed the area with RTV. Bad idea... That new sensor and one more failed in short order before I discovered my folly. So, I shelled out another $60 for a third sensor, and left the little opening alone. In the 5 years after it never failed again "AS IS".

[StickWalker]

I believe I found the issue. I did not realize how bad the TPS wire connector had become. I've replaced it and seems to be driving better

http://i609.photobucket.com/albums/tt173/jump150/TPS%20connector_zps29fuuv6e.jpg (http://s609.photobucket.com/user/jump150/media/TPS%20connector_zps29fuuv6e.jpg.html)

[XfireZ51]

[QUOTE=StickWalker;220044]I believe I found the issue. I did not realize how bad the TPS wire connector had become. I've replaced it and seems to be driving better

Occam's Razor.

[Johnny5]

"It appears that Z owners that is having the problem have in commons are: 1) the secondaries eliminated
2) Haibeck chip

How about the injectors. What injectors do you have currently installed. I have talked to Marc in regards to this concern and he has 2 1990 that are doing the same thing as well. He suspecting injectors. I'm going to data log and check the car out this weekend. Will let you know what I find out. We can make some changes to the fuel trim if need be."

I have a 1991 (27k miles) that is all stock so I did not delete the secondaries or have a chip. (The secondaries won't open up either) it currently has the stock injectors as well and I noticed my car bogs or surges when cold too! I'll see if it does this after changing the injectors. I just ordered the obd2 to obd1 conversion so i can see if I get any codes from my scanner.

[StickWalker]

I have new injectors from FIC that I installed this spring and maybe have 1000 miles on them now.

[secondchance]

"It appears that Z owners that is having the problem have in commons are: 1) the secondaries eliminated
2) Haibeck chip

How about the injectors. What injectors do you have currently installed. I have talked to Marc in regards to this concern and he has 2 1990 that are doing the same thing as well. He suspecting injectors. I'm going to data log and check the car out this weekend. Will let you know what I find out. We can make some changes to the fuel trim if need be."

I have a 1991 (27k miles) that is all stock so I did not delete the secondaries or have a chip. (The secondaries won't open up either) it currently has the stock injectors as well and I noticed my car bogs or surges when cold too! I'll see if it does this after changing the injectors. I just ordered the obd2 to obd1 conversion so i can see if I get any codes from my scanner.

Assumption that secondary removal and Heibeck chip causes stumble is not true. I had my secondaries removed and run Heibeck chip. I had stumbling problem but the issue turned out to be O2 sensors. Replacement of O2 sensors fixed the problem. After another couple of months stumbling returned. This time the cause was TPS going bad. MAP sensor going bad will cause the car to stumble also. Bear in mind that our cars are 20 plus years old resulting in some sensors giving up the ghost.

Done correctly, secondary removal and Heibeck chip to run both injectors are worthwhile modification.

In your situation, with OEM injectors, I'll bet your injectors are failing. I've seen enough ZR-1s with OEM injector failures.

[XfireZ51]

"It appears that Z owners that is having the problem have in commons are: 1) the secondaries eliminated
2) Haibeck chip

How about the injectors. What injectors do you have currently installed. I have talked to Marc in regards to this concern and he has 2 1990 that are doing the same thing as well. He suspecting injectors. I'm going to data log and check the car out this weekend. Will let you know what I find out. We can make some changes to the fuel trim if need be."

I have a 1991 (27k miles) that is all stock so I did not delete the secondaries or have a chip. (The secondaries won't open up either) it currently has the stock injectors as well and I noticed my car bogs or surges when cold too! I'll see if it does this after changing the injectors. I just ordered the obd2 to obd1 conversion so i can see if I get any codes from my scanner.

I have secondaries removed for many years using my own calibration.
I don't have any bog. Just sayin.

[rkreigh]

I have no issues with the secondaries gone other than the simplified maint and increased performance

it's not a good idea for passing emissions but the lt5 don't need no stinkin secondaries IMHO and marcs cal is spot on with this mod

don't expect too much in terms of additional hp unless you really open up the ports in the head to take advantage of the intake porting

even without the additional porting, I like the sharper throttle response, increased mid range torq (about 8 fts on the lt5) and likely about 5 hp up top

the flappers are only a few cfm in restriction but they really are better off gone and passed on to someone who wants to keep the car stock

very happy I did this mod with Marc. get rid of the air pump too and lighten up the car

"parts left out don't break"

it's not a hack, it's a really nice mod

[Hog]

I don't think anyone would see any negatives with a good ECM recalibration, such as a Haibeck chip.

[Johnny5]

I was quoting someone else to say that my secondaries are not deleted and it does bog occasionally

[Paul Workman]

"It appears that Z owners that is having the problem have in commons are: 1) the secondaries eliminated
2) Haibeck chip



Apples n oranges... At issue is bogging upon acceleration. The occasional stalling on de-cel has a different set of circumstances and characteristics; perhaps coincidental to secondary delete and Marc's calibration. But, it is certainly NOT a new phenomenon, and NOT exclusive to the LT5 at all.

And, with regard to deleting the secondaries, in many cases, it is often in conjunction with some amount of porting; porting which alters the AF requirements a bit which may well "poke the bear" a bit.

So, IMO it would be a mistake at this time to make attempt to codify a connection between the secondary port throttle (SPT) elimination OR Marc' calibrations exclusively (others do both as well). Juuuust sayin.;)

[Johnny5]

Ok, so i was replying to Bennie C on Page 2 quoting him that all these issues were from deleted sec, and chip. I stated that mine does that and i have neither. So i dont believe that is an issue. My 91 is stock, i believe i have an injector and/or pump issue. Waiting til Spring to do a tuneup.