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Discussion Starter · #1 ·
Hello all,

Just want to preface by saying THANK YOU to everyone who posts here, I've almost always found the perfect/quick/cheap way to repair a problem myself without having to take my car in to a shop.

I'm having an issue now that I haven't really been able to fix. Mine is a 1991 N/A Automatic (2.3) with 180,000 miles and a recently done major overhaul (basically 6 hours every weekend since August). For the most part running great now that the engine is back together, but now that the weather took a sudden dip I'm noticing an issue at idle. When the car is cold, it's worse, but it does it when warm too:

The needle wants to stay around 1,000rpm, but every couple seconds or so the needle blips up to maybe 1150 then drops to 900, then back to 1,000. Repeats indefinitely, and is accompanied by an audible note change from the exhaust as well as a change in vibration from the engine, almost as if it was skipping a beat. Also sometimes, only when cold, the first time stepping on the gas pedal (like to go up a hill or pull out of a parking lot) the rpms drop to maybe 400. Feels like it wants to stall but it never has. And it only happens that one time. When driving, the car runs smoothly with no noticeable issues. Finally, whenever the radiator fans kick on at idle the car shakes and rattles for a second before settling down. Not sure if this is even all related...

I put in new sparks plugs when I installed the cylinder head, but I know that people have different preferences ranging from .89 to 1.1. Worth it to regap?

I have a spare DI cassette, would it be worth it to give that a shot?

I tried the trick of spraying carb cleaner around vacuum hoses (I hear a hiss from behind the manifold that I thought might be a leak) but there was no change in idle.

I could clean the IAC/AIC valve, but I'm actually not sure where it is located.

Any thoughts on which seems most likely, or other ideas altogether?

Thank you!!
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