KITT87

Hey all, I’m going to be going through the service manual for this problem soon, but I wanted to put a thread out there in case anyone has dealt with it before. Car is 87 base Firebird with the V6.

The car drives fine until it’s warm. If I accelerate from a stop when the car is warm and it was idling low, it will misfire a few times before driving like normal. The cold/high idle in park is fine, but when it’s idling low/hot it rises and lowers by about 100rpm repeatedly. It also will not idle low unless you give it a little gas (although it randomly will idle low by itself sometimes). I feel like it takes a while to warm up but that could be just me or the time of year.

So far I have:
- gotten a new distributor and set the timing (replaced due to unrelated issues)
- put on a new set of spark plug wires (again due to unrelated issues)
- cleaned off the IAC valve and the intake
​​​​​​- replaced the PCV valve and grommet
- did the “tap test” on the MAF (it passed)
The spark plugs have not been replaced (yet) and are 3 years (30,000 miles) old. I had them replaced not long after I got the car in 2021. I do not think there are any vacuum leaks but you know how that goes. The car is throwing no codes.

Has anyone experienced this before and/or have any suggestions for what to look for when I dig into it? Thanks!

KITT87

Small bump, did the rest of the tests on the MAF today, it checks out and works fine. Moving on to the TPS tomorrow and the plugs Saturday hopefully. As I said, if anyone has experienced this before please drop a response in here, would sure help me out.

Vader

Do you have a fuel pressure measurement to share?

KITT87

Unfortunately I do not own a kit for testing fuel pressure. I’m going to try to get one when I get paid (next week), or try to rent one from an auto parts store. I know this doesn’t change anything but the fuel filter is brand new.