Hello! I've inherited a 82 trans am that the rest of the family has given up on. The idle issue is a ongoing problem which has let the car sit for the past 5 years, it was sitting for 20 years or so years before that.
I'll try to be as detailed as I can! Sorry for the wall of text incoming.

Main issue : has random high idle. Seems to happen more often when spiriting driving rather than putting around. Will idle up to 1000-2500. If the key is cycled it idles right back down to normal. I can shut the car off at a stop light and quickly restart it and it will idle back to normal, until more spirited driving. Does seem to happen slower after I restart it hot rather than cold starts. Some days it happens after the first heavy acceleration, some days it takes 20-30 minutes of harder driving. I can cruise it around like a old"er" person and it sometimes doesn't happen at all.
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​​​​​​Only other issues really are after a cold start, the first moderate to heavy throttle application, like pulling out into traffic. it almost dies for 2 seconds or so, if more gas is given it drives through it and doesn't have the issue again, until another cold start. I don't remember it happening on hot starts(when I cycle the key at stop lights to fix the idle issue it doesn't bog down). This is a somewhat newer problem from the high idle issue, and unsure if it's related.

Also just seems to have a lack of power, it's not a snail, but it won't peel out on a wet road or anything.

​​​​​INFO! 82 trans am, crossfire 305, many things have already replaced, entire fuel system from the fuel tank to lines, injectors cleaned professionally, with the larger fuel pump. Fuel pressure increased to 13 psi. Newer cap, rotor, plugs, looks to be a newer distributor. Ecm replaced, map sensor replaced, throttle body's rebushed. IAC's replaced, I cleaned the originals he still had in a box of parts and reinstalled those. (All done 5-6 years ago before it sat).
I rebalanced the throttle body's and set timing to 8degrees. Smoke tested for vacuum leaks. I checked for correct voltage at the ECM, and cleaned the grounds. Set TPS.
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​​​​​I Appreciate any info!
Thank you!

 

1. How old are the usual "tune-up" items--O2 sensor, distributor cap, rotor, plug wires, spark plugs, fuel filter, air filter, initial timing checked, electronic timing advance verified, checked for vacuum leaks, throttle body cleaned, etc.? Lotsa stuff got replaced, but was this 5--6 years ago?

2. What is the fuel pressure at prime, at idle, and under load?

3. Connect a scan tool, verify EVERY sensor and computer output. Look at the short- and long-term fuel trims. Capture a record of the computer system inputs and outputs while the vehicle is acting up. In particular, does the coolant temp sensor provide the computer with accurate temp information, same for the TPS, and does the IAC work properly?

4. How old is the gasoline? "I" would be assuring that only Top Tier fuel was used, and for the first few tankfuls, a bottle of Techron Complete Fuel System Cleaner was added. Again, tank and fuel system was replaced, but was this 5--6 years ago, and now that gasoline has turned to varnish?

 

Thanks for the reply!
I Replaced the O2 sensor and throttle position this past weekend. I thought it fixed the issues but they returned by wed/Thursday. It for sure has more power, but the idle and stalling issue remain. (I just drove 15-20 minutes to work daily). Everything is for sure 5 years old. I did forget to mention I drove it from my uncle's to my house 800 miles! It probably has around 900 or so after I picked it up.

I have ordered the tune up stuff, as one of the spark plug wires was a bit close to the manifold so I can post updates after that! I did smoke test for intake leaks but didn't notice any.
I Did check fuel pressure this week only at idle, and found it pretty high, bouncing around 15psi, I did lower it to around 12-13, as I read that's were crossfire's like it? My only worry is it does have a larger pump installed so maybe it still a bit too much fuel at 13?
I ordered the DLC cable yesterday so I'll give more info on the data list when that comes in.

​​​​Ive only ever put 93 in it, but last tank i used ethanol free 93.
​he mentioned it doesn't do well on anything but. I set timing to 8 degrees today as it was sitting around 1-2 or so, but have not checked it advancing or anything. I have not noticed any pinging/spark knock sense I advanced it.

I'll update when I have more Info! Thanks!


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Is the fuel pressure gauge accurate?
If the fuel pressure can be lowered at idle, the return side plumbing is not too small. Therefore, there is no concern with "too much fuel" as long as the pressure is adequate.

Ok.

I wasn't suggesting anything about octane rating, although that's important. I'm concerned about DETERGENT in a fuel system that's been parked as long as yours.
AGAIN, dump some Techron in the tank, and buy your fuel from a station that advertises Top Tier fuel.

I don't know what reasonable initial timing is on that vehicle. 8 degrees of advance would be too much for my truck, but it does like more than the emissions sticker calls for because I have aftermarket heads. I run 4--5 degrees of advance rather than the "0" it calls for.

 

F'n gasoline has NOTHING to do with this issue. There is no need to waste your money on "Top Tier fuel"

OP; have you checked to see if you're TB's are binding? My CFI TB's at one point, were worn, the throttle blades would catch in the bores differently when you closed the throttle, depending on how you did that....and cause high idle. I'd start by checking there.

I'd also advance the timing more. CFI timing is way too conservative. Mine "liked" ~12*.