1984 Fiero SE 2M4 Sudden Idle Spike/Surge (Page 3/3) Sanhino MAR 18, 04:05 PM Alright another update: I replaced the temp sensor to ECM, spark plug wires, and distributor cap. I wasn't able to double check timing since my timing gun was in my other car and I took my work truck home today, but after starting and idling at about 1,500 rpm initially for 30 sec. or so, once it got a bit warmer it went down to about 800 rpm and stayed down. I shut the car off and started it again about a minute after and immediately after starting it, it crept up to about 2,300 rpm and stayed there. I mean I'd rather it be idling high and be able to use it but it's still irritating knowing it's not right. Sanhino MAR 22, 12:35 PM So I went through and tried to clean most of the electrical connections of any gunk that was in them, and cleaned the engine grounds and the starter connections. Overall they weren't too bad looking but it sounded like a good idea. I started the car and after reaching temp it was idling at about 900 rpm, and I checked the timing and it was low, I can't remember what number but it was like 4 or 6 degrees or something like that. I noticed as I advanced the timing even just the slightest amount it caused the idle to spike to about 2,300 rpm. It seemed like just the slightest amount of movement from the distributor cap caused it to spike, but I'm not sure why. Eventually it calmed down and idled back at around 900 rpm again but I didn't particularly do much to cause it to go down, it just seemingly went back on its own. phonedawgz MAR 24, 10:37 PM The ECM is supposed to adjust the idle speed back to 900 RPM via the IAC.