Hey guys, I have a 91 Z28 5.0 5 speed, all stock just exhaust and pulleys. I just recently put new bosch 3 injectors in it along with a new egr valve, tps, coolant temp sensor, iac valve, ecm, and did a tune up as well. my issue is only when it goes into closed loop and i pull up to a light or stop, the car will either randomly die or the rpms will drop to around 400 and then it will try and stall. it always starts right back up but it will die as soon as it starts to idle. it also seems to happen after i go on a drive and shut it off, then i start it back up and it will usually fire and die right away. i have to feather the gas to get it to idle, but as soon as i start driving it is perfectly fine, the idle is the only issue. i'm lost ive replaced so many parts and the car runs great except for this issue. i even took out the hypertech chip it had in it and set the timing to the stock 6 degrees advanced. Any ideas??? any help would be greatly appreciated!

 

I would check operation of your TPS sensor, I know you replaced that , but check the voltage on it. Also check you IAC again, and you need to get a someone to use a scan tool and check the IAC count and make sure it is correct. That would be where I would start. Also, check for vacuum leaks, and that the throttle body is clean including the IAC port. Hope that helps some....

 

what should the voltage be on the tps? Is there any way to check the IAC without a scan tool? I did check for vacuum leaks and didn't find any, i used starting fluid and sprayed around all of the areas, didnt come up with anything leaking, is there a better way to check for leaks? Thanx for the info!

 

TPS voltage doesn't matter on a 91. The computer assumes the voltage at power on is idle. In fact the correct TPS sensor for a 91 doesn't even have adjustment slots. 9 times out of 10, idle problems are related to the IAC. Remove the IAC, spray out the passages with carb cleaner, spray off the IAC pintle, and reinstall the IAC. That usually fixes it.

 

yea my tps is not adjustable. the IAC is only like 6 months old but i will take it out and clean everything up and see what happens. Thanx

 

While you're at it, clean the throttle body and the back side of the throttle blades. Sometimes you'll get a build up that causes problems.

 

yea when i did the injectors i cleaned the throttle body, plenum, and runners out pretty well so it should be clean already, but i guess it wont hurt to look at it again when i take out the IAC. car runs great besides this stalling issue