When I start my engine, it idles all weird. It will drop to as low as like 400 rpm, then jump to 1500 without me touching the pedal. It's a fresh o2 sensor, and fresh gas with fuel system cleaner in it. The car had been sitting for about 2 years, but the tank was only about 1/8 full before I filled it up with 91 octane. 87 tpi 350. Stock except for shorty headers and short ram intake. Once engine gets to temp, it idles normally. Anyone know why it's idling weird when engine is cold?

 

Cleaning and lubricating the IAC pintle may resolve that problem.

 

Really impossible to tell what problem is without a log file.

 

 

Same issue with my stock 88 lately. First cold start hits right off but sags then comes up after a few seconds. Checked all over for vac leaks,new hoses and spring clamps where they would work. New last year injectors,plugs,wires, new Delco sensors, air temp, coolant, tps,egr and so on. Timing perfect all temps seem correct on a scanner when cold, nothing jumps out as being way off. Throttle body clean, tps at .54, re did minimum idle ok. Iac seems ok but does push in real easy compared to others I have had, some turn. Anyone have an idea what a good count number should be for the tps to start? I know varies car to car. I thought the snap on scanner said 140 ish, full warm idle was down to about 8 I think. Read article said no less than 4 or damage to iac. 305 tpi automatic. Dont remember it doing this last year for the little I drove it. Thanks Allan