Weird idle when engine cold
07-30-2018, 08:09 AM
#1
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Location: Minnesota
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Car: 1987 Firebird Formula
Engine: 350 TPI
Transmission: 700R4
Axle/Gears: .373
Weird idle when engine cold
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?
Last edited by Zell1luk; 07-30-2018 at 08:26 AM.
08-05-2018, 07:49 PM
#3
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Re: Weird idle when engine cold
Really impossible to tell what problem is without a log file.
08-05-2018, 08:59 PM
#4
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Car: 1990 Trans Am
Engine: 5.7 350 HSR afr195 xfi268
Transmission: T5
Axle/Gears: 3.08 posi
Re: Weird idle when engine cold
I agree a log would pin point what’s happening a lot easier, but I agree with Vader’s start with iac...sounds like it might be sticking initially and finally stabilized at closed loop ...that would explain a vaccuum like symptom your having that disappears once close loop happens.
08-06-2018, 06:29 PM
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Re: Weird idle when engine cold
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
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