All,
I have been tying to find an answer to my problem with no luck. My 88 IROC 5.7 engine was failing so I decided to have a ZZ4 installed by the local shop. To accommodate the swap, a new intake, 24lb injectors from TPIS, and an updated prom from TPIS to handle the EGR delete and 24lb injectors. The car starts immediately and then stops. I can keep it running briefly if I stay on the throttle, but eventually it stalls. While running it sounds good. Note that the car will run very roughly and richly with the MAF disconnected.

Here is what I have done/checked to date:
1. Codes = TPI voltage was high, which I corrected. Other than that just the normal code 12
2. Fuel pressure = OK
3. Swapped out the MAF = same behavior
4. Checked vacuum lines = looks OK.

Any guidance would be welcome. Thanks in advance.

 

FYI - ON #1 I meant "TPS" voltage was high.

 

When you say the TPS voltage was high - what was it at. I think the TPS voltage is supposed to be around 0.54 Volts +/- 0.61 Volts.

Try checking it with a multi-meter and she what it's set at. Have you checked or reset your IAC?

Make sure there aren't any leaks in your intake track. Leaks can make the MAF have a fit and have a rough idle and die if it's bad enough.

 

Good points re: the TPS and IAC. Make sure to properly set the TPS. Once set disconnect the battery so that the computer will clear and reconnect it and try to fire it again. After re-assembling mine after replacing the injectors it didn't run right.

 

yaj15, and IROC giraffe,
Thanks. The TPS was at .61, it is now at .54. The IAC was replaced last year. I'll look up how to reset it and get reply in a few days.

Thanks,
FP

 

http://www.chevythunder.com/do_it_yo...ation_page.htm

Check out this link. I had the same exact problem late last year with my car. I got my plenum ported, SLP intake runners ported to match and a base plate.

I'm still running the stock L98 long block in my car and the way my car ran it sounded like I had a high lift short lsa racing cam. My car was also running really rich.

I had to reset the IAC and the TPS several times for it to start running right. The MAF cars are real sensitive to any intake changes. The smallest issue can make the entire system not run the car right at all. The speed density cars aren't as sensitive to intake changes as the MAF cars are.

 

The higher 0.61 TPS voltage should make the car feel a little more responsive. Since that was still within specs hopefully thats not the problem. Could be the IAC or something simple like a vacuum leak too.

 

Other way around.
A MAF setup measures the exact airflow into the engine so the ECM can (within reason ) make fueling adjustments automatically
for any airflow changes resulting from a bigger cam , better flowing heads / intake

A MAP (speed density ) setup "guesses " the airflow based on the intake manifold pressure so they are less able to "self adjust"

 

All,
The IAC was at 1 and 1/8. I adjusted it back down slightly. No change in symptoms.

Thanks,
FP

 

Sounds like the IAC was not properly set. Kinda tricky, and you may have to set it and the TPS a couple of times to get it right. Here's the procedure.
https://www.thirdgen.org/tpimod2

Also, the TPI is very sensitive to vacuum leaks. I thought I had done mine perfectly, but still had leaks at the runners. Had to take it apart and re-seal, using a little RTV on the (new) gaskets for insurance.

 

All,
I attempted to go through the procedures suggested by Darbysan. However, all I could do is jumper the A&B and then yank the IAC cable. The car started as usual and died as usual.

Note: I was able to capture some data with Tuner Pro albeit at the lower 160 baud sample rate (data samples every 1-1.5 seconds or so). Not sure what I am looking at, but at least I can compare it to pre engine swap data captures. I have this all in Excel if anyone want o take a look.

Thanks!
FP

 

Briefly try the stock PROM chip to rule out an issue with the prom or a corrupt/wrong calibration. Also is the timing set correctly at 6-10* BTDC with the timing wire disconnected. It sounds like the timing might be off. MAF cars are also very sensitive to small vacuum leaks. I would look for disconnected hoses such as a/c, power brakes, pcv, pcv vent, etc.

 

 

Yeah, I'd try the stock chip.
I'm not a fan of mail order tunes.

 

Are you still running the EGR system or did you get rid of it all together? The ZZ4 heads are the same aluminum heads that came on the L98 Corvettes.

They don't have an internal exhaust gas cross over tube like the cast iron f-body L98 heads do.

The L98 Corvettes have an external EGR system and you might need to run something similar for your car.

 

I am going to swap out my built L98 for a ZZ4 but I have worried that I am going backward instead of forward. Hopefully there are no issues placing my corvette TPI on the ZZ4 and later build up on that.

 

All,
Thanks for your replies. I have given up for now and went to a carb setup. I'll go back to the TPI intake at some point, but possibly with a Holley or FAST retrofit ECM. I just want to drive and enjoy it for now.

Thanks,
FP