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1988 Iroc Z 305 idle problem

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Old 11-16-2017, 10:01 PM
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1988 Iroc Z 305 idle problem

I have a 1988 Iroc Z TPI with a 305 and a 5 speed. I'm trying to figure out what the car should be idling at. I have cleaned the throttle body and replaced the TPS and IAC sensors. It is idling around 750 RPM but seems to be running really rich. I'm all out of ideas and in desperate need for some help.

Last edited by ws6yeats; 11-16-2017 at 10:13 PM. Reason: Misspelling
Old 11-17-2017, 08:45 AM
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Car: '86 Iroc Z & '91 RS
Engine: 305 TPI & 305 Qjet - Future LC9
Transmission: 700R4
Axle/Gears: 3.23
Re: 1988 Iroc Z 305 idle problem

I'm running a 89 tune in my 86 to delete the 9th injector, still smells rich on a cold start until it gets up to opetrating temp.. check your voltage at the tps and reset the iac maybe?
Old 11-17-2017, 08:54 AM
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Re: 1988 Iroc Z 305 idle problem

The voltage is sitting right at .54 on the TPS and I also have reset the IAC. It seems like it like to idle around 850 RPM without smelling unburned fuel but then again the tach may not be accurate. I'm just running out of ideas
Old 11-17-2017, 11:45 AM
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Car: 1967 Camaro, 91 z28
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Re: 1988 Iroc Z 305 idle problem

You might want to get a fuel pressure tester. Watch after prime is the pressure drops. If it drops fast you have leaking injectors or a rip in the fpr diaphragm. To check the diaphragm pull the vacuum hose going to it and look for raw fuel.
Old 11-18-2017, 05:23 PM
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Re: 1988 Iroc Z 305 idle problem

I noticed today that if I put a paper clip in the A and B port on the ALDL and unplug the IAC harness that the car idles perfect. I'm starting to wonder if the new IAC valve I put in is defective. I have verified that I don't have any vacuum leaks. I'm trying to get my hands on a fuel pressure tester
Old 11-19-2017, 09:45 PM
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Car: 1992 Z28 and 1995 Silverado
Engine: 5.7 TPI and 5.7 TBI to TPI convert
Transmission: 700R4 and 4l60E
Axle/Gears: G80 3.23 and open 3.42
Re: 1988 Iroc Z 305 idle problem

A cheapo bluethooth aldl 'scanner' from ebay will tell you loads of stuff you need to know.
Also maybe you didnt reset the IAC correctly.




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