90 - Running out of breath at 5000 - No Codes
 

Trying to figure out why my 90 5800 mile ZR1 (new owner) completely runs out of steam at 5000 RPM, it doesn't pull particularly hard to that point and really badly from 4000 RPM.

Background:
I previously had a code 61 - which I ended up replacing the solenoid, vacuum canister and secondary plastic piping. I checked the actuators and both openned quite easily. The car no longer throws a 61. When reassembling the solenoid had an extra nipple which I plugged (don't do this). which led to a hard code 56. Upon removing the plug, the 56 has gone away. The only modification that the car has is a Haibeck chip which is slightly detuned to handle the 90 Octane ethanol free gasoline.

I'm a bit of an odd case judging by other forum members in that I have original injectors, I don't believe the car should have injector problems as it has always run ethanol free gas. The fuel I'm using currently is 90 Octane Ethanol Free, as sold at a local Sonoco station.

Anyway, at this point I'm not getting any codes coming back. I've attached a datalog from datamaster. Its short and hopefully it tells enough of a story. Anyway, any assistance would be greatly appreciated. I haven't owned the car since new, so I can't say I know what a clean pull feels like, but as it stands the car quite often feels like it hesitates, and even at times it feels as though spark is cut momentarily then the car starts to pull again.

Any thoughts would be greatly appreciated.

Re: 90 - Running out of breath at 5000 - No Codes
 

Sounds like the secondaries are not operating.

Re: 90 - Running out of breath at 5000 - No Codes
 

Thanks for the input. My thoughts are identical to yours... I just am at a loss as to how to get them to open. Especially given the actuators work, no code 61 and in the datalog, the ECM thinks the secondaries are open.

Does anyone know where in the FSM to look, or a local to Tampa/St Petersburg/Clearwater expert to talk to. I'd love the satisfaction of fixing it myself, but the end goal is to have another well running Z on the road.

Re: 90 - Running out of breath at 5000 - No Codes
 

Assuming you have a "FULL POWER" indicator when the secondary's switch is ON, no codes, then I wonder now if you've got the "accordion" plastic intake tube is collapsing syndrome.

Mine was collapsing, at around 5000 rpm and falling on its nose too. It is a common problem with those old plastic "snorkels" - especially when the under-hood or ambient air temps are on the warm side. However there is cheap and easily fixed either by installing some of Marc's wire hoops to support the tube, or do as I did and build a sheet metal sleeve that slides inside the tube to smooth the air flow and keep the tube from collapsing.

Just a thought!

P.

Re: 90 - Running out of breath at 5000 - No Codes
 

Good thinking Paul, does the new owner know how the seconday key works, and there is a light on the DIC that says "Full Engine Power"

Re: 90 - Running out of breath at 5000 - No Codes
 

Hi Paul,

I will go out and purchase a stocking, make a temporary air filter and eliminate the snorkel to see if that is the issue. I have doubts on the snorkel theory as the car is smooth to 4500-5000 ish with the power key off, when the key is in the full power position, the car does all kinds of miss behaving prior to hitting the 5000 mark.

Thanks for the input, I'll likely get to this around Wednesday... have lots of crazy project work to do this week.

Thanks again
Jonathan

Re: 90 - Running out of breath at 5000 - No Codes
 

Yes, sir the DIC shows Full Power. I would say that the key isn't perfect though, as I turn the key to where the on should be then have to rotate it back a smidge to get the light to turn on. Not sure if its possible that it could be switching states while driving, but the light stays strongly illuminated.

Best Regards
Jonathan

Re: 90 - Running out of breath at 5000 - No Codes
 

My key can be a little tempermental. I think the contacts are dirty. I have to cycle the key sometimes to get it to activate

Re: 90 - Running out of breath at 5000 - No Codes
 

My key did the same thing until I took the switch apart and repaired/adjusted the contacts. It is important to the ECM that the switch is not flaky.

Re: 90 - Running out of breath at 5000 - No Codes
 

So, I looked through the datalog and noticed a bunch of knock. I put original PROM back in... things seemed better right off. So then I went to go drill it.

Code 61 - 5K max, but relatively smooth compared to before. So now what, did I install a faulty solenoid? bad vacuum canister? ECM?

Any thoughts on what I'm missing apart from the 5 hrs on Sunday. I really thought I got that 61 and fixed it.

Re: 90 - Running out of breath at 5000 - No Codes
 

SECONDARY PORT THROTTLE VALVE SYSTEM error
But of course you know that.

Try seeing of the actuators pull in
http://www.zr1specialist.com/HAT%20W...0Operation.pdf

If they do maybe your secondary fuel pump is tits up.
You could be running out of fuel but no code is set if it's not
lean enough to trip the code.

Re: 90 - Running out of breath at 5000 - No Codes
 

Thanks for your help with this problem. I have performed the check by shorting pin C17... unfortunately everything worked as it should, so now to keep checking till I find something.

I don't have equipment to check the fuel pump... so I'll have to take it in sometime this week. Thanks for the input.

Re: 90 - Running out of breath at 5000 - No Codes
 

Open the hood.
Engine off but ign key on.
Does the vacuum pump under the passenger side head light run?
Does it keep running without shutting off?

Re: 90 - Running out of breath at 5000 - No Codes
 

It runs for a moment then stops.

FYI - the shorting of C17. While the actuators are moving, the pump runs, then shuts off again. Actuators stay open for as long as I'm patient enough to short the circuit.

Re: 90 - Running out of breath at 5000 - No Codes
 

Sure sounds like secondaries are fine. Look to fuel pump #2 failure.
The only thing that puzzles me is that I'd expect a lean code to be set.

Re: 90 - Running out of breath at 5000 - No Codes
 

A lot of preliminary stuff can be done at home. (Besides, I don't know 'bout your situation, but there isn't any dealership I'd take an LT5 to for anything!)

As for checking the fuel pumps, all you need is a fuel pressure gauge that you can rent free from AutoZone** and a Volt Ohm Meter from Radio Shack or the like.

You can start by measuring current draw to the pumps. There is a fuel pump test connector jutting out of the same wire loom as the diagnostic connector, located near the top of the power brake booster, next to the firewall.

With the key off, and the VOM configured to read Amperes (most set up to read 10A) put the red lead to the positive terminal of the battery and the black lead to the little red pigtail. Each pump draws between 4-5A. So,if both pumps are running normally, you'll measure between 8 and 10 amperes, you'll hear the pumps running, and with a fuel pressure gauge connected to the Schrader valve, fuel pressure should be about 52 pounds, give or take a pound or so.

Configuring the meter to read amperes...

http://i185.photobucket.com/albums/x...ntcheck004.jpg

The red test connector connected (via a yellow jumper with alligator clips on each end - alligator clip leads available from Radio Shack) to the black lead of the meter.

http://i185.photobucket.com/albums/x...ntcheck001.jpg

With the red lead connected to the positive post of the battery, the current draw is normally 8-10 amperes if BOTH pumps are running. If only 1/2 that current is present, then one of the pumps is either kaput or there is a connection issue (possibly).

http://i185.photobucket.com/albums/x...ntcheck005.jpg

Then you can check the fuel pressure under driving conditions, by taping the pressure gauge to the windshield and monitoring the pressure at normal load and at WOT.

http://i185.photobucket.com/albums/x...PtestLarge.jpg

Pressure should be in the mid 40s in normal driving loads, and "pop" up to 52 (give or take) at WOT.

If the fuel pressure is low, especially at WOT, it could mean a problem with a pump, OR the fuel filter. (The filter is next to the frame rail behind the right front tire, and under a heat shield.)

Since the secondaries tested OK, you might want to know what the resistance is across the injectors when they're HOT. They should read between 12-14 ohms (hot). If they read 10 ohms or less, it indicates problems likely. A reading of 8 ohms or less and the injector is definitely in need of replacement; not only to run better, but to prevent the possibility of a burnt valve (ask me how I know...). (The procedure is well laid out in the FSM.)

And, of course, the easy thing to do is change plugs.

Re: 90 - Running out of breath at 5000 - No Codes
 

absolutely phenomenal wright up Clear easy to understand and easy to read

Re: 90 - Running out of breath at 5000 - No Codes
 

Scott and Paul, thanks for the help. I've done some testing...

The good:
Bought a fuel pressure guage, hooked it up.
46 PSI when can is not on, 41 PSI when car has been started and was running. FSM and precious comments in this thread indicate 48 - 55 PSI before start up as the correct measurement. So its a bit low. As you know this doesn't necessarily test the secondary pump, unfortunately I couldn't find and extension pipe.

The Bad:
I couldn't get a reading on my Multimeter (testing red pig tail, on mine it appeared orange and black... not sure if I had the right one, but the location was identical). probably doing something wrong.

Next steps:
With the pressure being low, I'm going to buy a new fuel filter, and 2 pumps. Hopefully in a week I can report back and say its happy days. Its going to be a big week for the little Z, it should have new shoes arriving this week.

Thanks again for all the help, if the plan of action doesn't make sense please let me know.

As for dealers... I've found a locally owned not Chevrolet dealership that keeps me quite satisfied, prices aren't that dissimilar to a dealership, but I trust them and that's more important to me.

Re: 90 - Running out of breath at 5000 - No Codes
 

You know best, but these cars are older than a lot of people working at some shops, and most(?) have never seen an LT5 before. These pages are filled with horror stories. Just sayin. SGC is Georgia, if that helps.

As for the high pressure reading, depending on whether there is perhaps air in the fuel line, the pressure may not peg at the 55# due to the secondary pump is shut off in a couple seconds. With the ignition switch OFF, connect the positive terminal of the battery to the red test connector on the wire loom and see what your fuel pressure is then. After a couple seconds, with both pumps running, the pressure should be in the 52-55# range. If it is, then the pumps are running.

However, see if you can find an extension (got mine at AutoZone too) to observe dynamic fuel pressure. Only then you will know if the system will provide fuel at the rate required at WOT. If, for example, the fuel filter is choked up, the pressure will drop across the filter, indicating the pumps are probably OK, but there is a flow issue.

Change the pumps if you want. But, I hate to see you changing parts in place of troubleshooting. That is how unforeseen variables get introduced to the initial issue, e.g., infant mortality, is the term applied to new parts that failed "out of the box".

Good luck!

P.

Re: 90 - Running out of breath at 5000 - No Codes
 

41psi is not low. It's way low.
Yes fuel filter on GP first if you're not sure how long it's
been but note likely the issue.
You're sitting right on the problem I'd say.
One or both fuel pumps. If you get 41 at about idle
imagine how it may drop off under high demand.
Best investment would be an extension and some tape.
Seems prudent before proceeding.

A note about the pig tail. It's the only one at that
location so unless someone added something you've got it.
It ONLY works as a test when the key is off. It does nothing
with key on because the way it is routed through the relays.
ALSO important to note with key off and applying 12v to the
pig tail you get BOTH pumps running. It's a great static test.
From there you can remove one or the other of the fuel pump
fuses to see what pressure each pump can do. You do not want run
these pumps for long periods of time through the pig tail. Just saying.... do each test, not the pressure and shut it off.

As for a place to work on your car. YOU will be the best influence
on how well they do with the car but you have to study up here
on the forum and show them the results.

Re: 90 - Running out of breath at 5000 - No Codes
 

Thanks for the insight on how the pigtail is intended to function, I'm a newb at this.

I've ordered a fuel filter, in hindsight I should have just bought one from a local store and had instant results. I will pickup the long hose likely today, and that way be able to run a test tomorrow (filter should arrive same day).

If it is the fuel pump. Which one should I get, I seem to remember running into a previous post of yours where you weren't such a big fan of the Airtex

On 06-12-2012:
"I wouldn't touch an Airtex ever again. My first "How to" on a fuel pump replacement ended in the Airtex failing. Maybe I just got a bad one but not willing to take a chance again. The flow rate on the P240KC is just fine for a stock engine. "


Would you recommend the P240KC or something else?


Thanks again to this community for being so helpful, experience really is the key to success with this IMHO

Re: 90 - Running out of breath at 5000 - No Codes
 

Suburban or Tahoe pumps work fine.

Re: 90 - Running out of breath at 5000 - No Codes
 

i thought 42 psi at idle was normal and 52ish when the secondaries kick in

Re: 90 - Running out of breath at 5000 - No Codes
 

I always tell people to be suspicious of any idle pressure below 43. It is one of those threshold values that should lead to more investigation. In my case it was a bad fuel pump that could not get higher than 41.
Easy to find out. Pinch the regulator vacuum. A really good pump will hit above 53 a mediocre one will be just above 50. Anything less than 50 is crap especially if it is new.

Re: 90 - Running out of breath at 5000 - No Codes
 

Yes that is my quote from a different thead. Aritex let me down. As for PERFORMANCE ELECTRIC Part # P240KC
I put two of them in a bit over a year ago and have been happy with them. Just yesterday I was testing them :p

Re: 90 - Running out of breath at 5000 - No Codes
 

My recent lack of power issue turned out to be bad ignition wires. And they only had about 8K miles on them.

Re: 90 - Running out of breath at 5000 - No Codes
 

So the potential fuel pump problem has been resolved. I installed 2 P240KC fuel pumps (if you are fearful of doing this, don't be it was very very easy - I have no prior experience with this stuff - <2 hours should probably be 45 minutes) and a fuel filter. Immediately after doing the swap I went for the excited test drive... same issue and saw a SES light very soon after start. Went home, hooked it up - Code 65 Rich Exhaust... I reset it and went for another test drive just to hopefully confirm the problem... Code 61 - Secondary Port Throttle.

Anyway, I'm a little confused as to what the problem is and where to find it. I recently replaced much of the whole secondary vacuum deal(solenoid and spider tubes). I hooked up the Tech 1 I recently acquired and noticed the Secondary Vacuum is 0 KPA. It does not move from this number. So I thought maybe I have a bad sensor, hooked up my handheld vacuum pump, and watched the secondary sensor work and show changes in vacuum in accordance with what I was doing.

So I feel at a loss for finding the leak. I've checked the pipe leading from the pump to plenum, and no leak also the vacuum pump does stop shortly after energizing and stay off. I had previously followed the code 61 instructions on this forum and I'm unsure of what I can do differently if I pull the thing apart again. Is there a good restart point or something obvious I may have missed. Any thoughts are welcomed.

Best Regards
Jonathan

Re: 90 - Running out of breath at 5000 - No Codes
 

I don't know if I can be of much help but looking at the FSM for a 1990 on page 6e3-c1-11and 12, It shows the vacuum and voltage at normal and full power switch settings. Normal mode should be 0.0 kPa and .54 - .62 volts at all times. Full power mode should be 33-66 kPa and 1.3 - 3.1 volts with the Tech1 tool.
You won't have full secondary operation if an engine code is present.
I am also wondering if the ECM is not recognizing full power mode for some reason even though the FP switch is on. Chart C1-F on page 6e3-c1-22.

Re: 90 - Running out of breath at 5000 - No Codes
 

Jonathan, here is way to operate the secondaries with the plenum in place. This will allow you to test them and actually see them pull in without rolling down the highway.

I agree with all in this article except the assertion that 1 sec cycle time on the pump is ok. It states that that having a longer cycle time does not affect the engine power. While this is correct, to leave a system with this amount of leakage is just asking for the pump to cycle itself into oblivion. I'd investigate and fix a vacuum system that cycled 10 sec or less. So anyway, try this and actuate the secondaries several times. If they seem to pull in on both sides, clear any codes then go for a drive and see. If it drops out again look to see what codes are set again and we can go from there.


http://www.zr1specialist.com/HAT%20W...0Operation.pdf

Re: 90 - Running out of breath at 5000 - No Codes
 

Thanks Franke, I went through the manual on these sections, and will go ahead an apply the FP test. If the rich exhaust comes back I'll run the other test. Thanks again for the input, and nice easy to get at locations in the FSM - I have a digital copy bought from WRP - and its a bit of a PITA to look at more than one page at a time.

Re: 90 - Running out of breath at 5000 - No Codes
 

Don! Three words. Secondary vacuum solenoid.

Re: 90 - Running out of breath at 5000 - No Codes
 

Hi Scott

Thanks for the info. FYI - car feels as though it starts quicker with new fuel pumps.

I've already run that test with success and it holds the actuators open as long as I want them to be open (was shorting the circuit on the front suspension arms). Pump runs while actuators are moving then shuts off again immediately and never turns on until the actuators are energized again.

These are the vacuum tests I previously ran:

Passenger side connector to the pump (by the oil filter), if I vacuum test it holds in both directions. If I pull the cylinder 3/5 vacuum pipe, it holds going down, but going into the plenum(metal side), I cannot get vacuum to hold.
Vacuum test Map sensor by the battery / ECM, the pipe does not hold vacuum, but the Map sensor does.
Vacuum test MAP sensor behind plenum, vacuum holds on the sensor, but does not hold going back into the plenum.

Don't think any of the above is a problem but in the interests of full information.

I think I'm going to try something ODD prior to pulling the plenum off again (its on the outer edge of my comfort level). Add vacuum to the sensor under the ECM, and pinch the pipe off when its in the range that Franke Specified, and then block the spider vein that would run to the sensor. My expectation is that and I am probably wrong... the sensor will be within range, the ECM will activate the secondaries and the pump will provide all vacuum necessary. If it runs well then I think the problem is somewhere in the spider vein headed to the sensor, but then again maybe not. This is not my area of expertise.

Thanks for the continued help
Jonathan

Re: 90 - Running out of breath at 5000 - No Codes
 

You will be an expert at the end of it all.
Can you confirm. No codes are set AND the loss of power is always at 5000rpm? (each and every attempt?)

Re: 90 - Running out of breath at 5000 - No Codes
 

I tried the
Surprise surprise - I was wrong :). So it immediately set a HARD Code 61, the ECM clearly is smart enough to know I was messing with it.

Anyway, I reset the code, hooked up the plumbing as it was before and. went for a ride. Car ran as before, with same symptoms. The code 61 is intermittent... meaning the code gets stored, it does not have the hard stop at 3000 rpm as you see when the service engine soon light is on.

So maybe I need to setup a video... the car accellerates, and it feels brisk, probably within a second it feels less brisk but continues accelerating to 4000 with some force from 4000 to 5000 acceleration is slow and at 5000 I run out of patience and shift (usually I'm in 1st and 2nd gear), as I'm in the city.

Easiest way to get the code 61 stored is to get on the the highway in a high gear at low speed and mash the accelerator.

- what does this test eliminate any items from the suspect list
- actuators [yes / no]
- solenoid [yes / no]
- reservoir tank [yes / no]
- front portion of vacuum system pipes [yes / no]
- check valve near solenoid [yes / no]

My gut feel says and the secondary vacuum number is the big clue, does anyone know perhaps if it stays at 0 kpa like mine does, and at which point that changes. ie does it change when the secondary pump charges the system or some other time. All I can think is something under the GD plenum is preventing Vac from getting to the Vacuum sensor under the ECM... there may be other issues as I recently replaced the solenoid, reservoir tank and spider hoses... so who knows.

There is so much info on this forum about the code 61, you would swear I was deaf to something or overlooked something.

Re: 90 - Running out of breath at 5000 - No Codes
 

Looks like you've replaced almost everything in the secondary's operation and your tests on the "plumbing" seem ok. Do you have a spare ECM?

Re: 90 - Running out of breath at 5000 - No Codes
 

I rebuilt my entire secondary vac system with brand new parts and after about 1 month one of the actuators went bad as well as the secondary solenoid. These were new items. I replaced the actuator with the old one, which was still good, and installed a new solenoid, and all has been fine since then.

I will bet that when you find the problem, it will be something simple.

Re: 90 - Running out of breath at 5000 - No Codes
 

There is another thing you should check. There are two check valves. One up front and one in back. The one in back is for cruise control which does not affect the secondaries. But the one that's up front can. It should only allow flow in one direction. So disconnect it and blow through both ports. If you can blow through both ports then there is some dirt inside of it causing the little BB ball to remain stuck. Just run some soap and water through it and blow it out with some compressed air. Then test it again.

Re: 90 - Running out of breath at 5000 - No Codes
 

Is this something I can do with plenum in place?

To be specific I'm trying to test :http://www.zr1netregistry.com/Portal...vachoseasm.jpg

The check valve located to the left of the tag in this picture.

Any way to do this with plenum in place? It will add about a weeks lead time in order to get gaskets etc to do this job.

Thanks for input.

Re: 90 - Running out of breath at 5000 - No Codes
 

No!

Re: 90 - Running out of breath at 5000 - No Codes
 

I assume your gaskets are original. Otherwise I just cut my own Felpro gaskets and reuse them. But my setup is a bit different then yours. I have finolic spacers sandwiched between the plenum and IH which blocks coolant from making it into the plenum. So I would just order the stock gaskets from Jerry.