1982 w/ a 1990 - 1992 TPI set-up

I'm trying to troubleshoot my car, it runs really rough and it has a slight miss. I have replaced everything...new heads, gaskets, ENGINE, distributor, rebuilt injectors, plug wires, plugs, cap, rotor, fuel pressure, checked for vacuum leaks etc.

I just noticed when I shut the car off, but left the ignition on I was hearing clicking / buzzing noise.....it ended up being the IAC valve.

Is it supposed to make a noise like that with the ignition on? It's brand new, but that doesn't mean a whole lot.

Thanks!!

 

It shouldnt be bussing. It may, just may, be trying to adjust itslef.
DO a resistance check, and also, check to see if it was installed at correct pintle length, per instructions when you bought it.
Here is a forum post I did a while back
http://forums.corvetteforum.com/c4-t...ac-is-bad.html

 

While it is running and at operating temps, why don't you put it in idle and tell us what you are reading for IAC counts? Maybe it is extended to the end one way and now that you are shutting down, it is trying to withdraw back to whatever point it needs to. Your IAC counts should be around 15-20 when the car is in idle and the engine at operating temps.

 

sounds like whoever wired the car left a positive wire that was supposed to be connected via the ignition switch wired directly to the battery, and when you shut the car off, the IAC is compensating for the engine not running, but the computer is still active.

 

Upon shutdown, the IAC is retracted to (in techo speak) to somewhere around 100 plus counts. This allows for a quick restart which will or should be at a higher rpm than when you shut it off. In terms of it running or buzzing, the process takes no more than 2 seconds and an acute ear (or an IAC on it's way out) might pick it up. If it's any longer than that, I'd surmise a busted IAC or ECM, assuming no idle problems which if there, you'd also want to check out the wiring.

 

Remember, Our IACS dont tell the ecm what counts it is running. When the scanning software is running, it only shows what the ECM is telling the IAC to do. Another GM oddity. The only thing you can do is a resistance check, wire check and pre install length test of the pintle.

 

I have an Auto X-ray and it tells me how many counts of IAC it is running at any given time. That is how I am able to set the min idle.

 

I will agree to disagree. Put a bad one in there and I bet it says the same thing. I have been doing this for a few years, and thought the same till shoebox showed me, here is his site, as he is on the camaroz28 forum. I had a bad idle for a few years. Never thought the IAC was bad, as I always had the "correct" counts. I was constantly beign told I had a vacuum leak or exhaust leak. Went round and round, and sure enough, the only thing auto xray, tts datamster LT1 edit do is read what the ECM is telling the IAC what to do, as it doent feed back to the ecm as it will never give you a code, as there isnt one.

 

Thanks for the info guys, looks like my IAC is working properly. Here's what I have so far:

Specs

Stock remanufactured 82 Corvette 350 Block and heads (less than 500 miles on both)

86 Corvette TPI converted to 1990 - 1992 Speed Density. 52 MM throttle body, heated o2 sensor.

Custom harness and all new sensors, including rebuilt and flow matched injectors

Stock HEI electronic distributor, plugs and wires (all new)

I also installed a CS144 alternator and upgraded the Big 3 so I know my electrical system is up to par.

I set the base timing at 6* BTDC with the est plug disconnected. I'm sure timing is right...I've done this many times so I'm a pro at it now.

My vacuum is showing 18-20....fluctuating between 18-20...not holding steady. It idles at approximately 750 rpm..but bounces to 500 rpm sometimes. Kinda bogs at idle, even when I'm not touching it.

My fuel pressure is holding a steady 39 lbs

I did a compression test and got

cyl 1 - 151

cyl 2 - 153

cyl 3 - 150

cyl 4 - 152

cyl 5 - 152

cyl 6 - 152

cyl 7 - 151

cyl 8 - 152

^ I think this is fine, to be expected for a brand new motor and heads.

I ran the car for about 15 minutes today to data log, when I turned it off...it would not start back up. I pulled the plugs and they had soot / smelled gas on them. I pulled them out to clean them. What could cause a rich condition like this?

I tried to propane trick to check for a vacuum leak, but didn't notice anything funny.

I have the stuff to data log and burn chips, I'm new at this so hopefully I can get this thing to run long enough to do a check.

One thing, about two months ago I went to a show in town..when I was leaving I got on the car a bit and it started acting funny. It died on me as soon as I punched the gas and I had to limp it home. I couldn't keep it idling or running, if I tried to accelerate it would die...I barely worked the gas to get it to move until I got to my driveway.

I need to double check my exhaust, it's "possible" that there could be a leak and screwing with my oxygen sensor, plus I welded the bung on myself and I'm not expert welder.

I hope I didn't leave anything out, if you guys have any ideas that would be great

 

Definitely check for an exhaust leak. Also make sure your O2 sensor is screwed in tight. Check your fuel pressure, as you may have a clogged fuel filter or bad fuel pump. Clear the codes before starting it up.

 

Ohm check the injectors.