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Engine run issue

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Old Jan 4, 2009 | 03:19 PM
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Default Engine run issue

My 86 Corvette starts, but must have the gas pedal depressed constantly to keep it running. Once moving, the car will drive forever. However, if I have to stop for a red light, etc, the engine will die, unless I keep applying gas. The car is fuel injected.

Any ideas?

Last edited by CooterTate; Jan 4, 2009 at 03:20 PM. Reason: Title was unclear
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Old Jan 4, 2009 | 03:40 PM
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When was the fuel filter last changed? Checked fuel pressure reading? Have you check the TPS setting? These would all have an impact on the idle of the car.
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Old Jan 5, 2009 | 01:17 PM
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If it runs fine off idle and won't run if you take your foot off the gas, check the idle air control motor. It probably died.
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Old Jan 5, 2009 | 04:12 PM
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fuel pump, fuel filter, alternator, plugs, wires, tp, maf, so many things
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Old Jan 5, 2009 | 04:28 PM
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At what RPM does it begin to have trouble?

A stock L98 in good condition should idle at 650RPM, I believe. Do you have to keep it above that, or can you hold it there with the throttle?

If you can hold the car at idle with the throttle, than I would suspect a dirty throttle body/IAC or dead/malfunctioning IAC. I would clean the throttle body/IAC and go through the base idle reset procedure (this will require some special tools, you can get them from a corvette supply house - corvette central, Mid America, etc).

If the car dies well above 650RPM, then you have a different problem, perhaps a vacuum leak, or spark issue.
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Old Jan 5, 2009 | 10:53 PM
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Let's start with the basics. How many pounds of fuel pressure do you have on the fuel rail @..

Initial key on.
Idle (or as close as you can get)
Under load.

Tape the gauge to your windshield, tell me what you've got. We'll go from there.

I honestly suspect a dead IAC, but I want to rule out other fuel system issues first.
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Old Jan 5, 2009 | 11:48 PM
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JMO...... MAF related.
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Old Jan 6, 2009 | 08:46 AM
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Originally Posted by Square
At what RPM does it begin to have trouble?

A stock L98 in good condition should idle at 650RPM, I believe. Do you have to keep it above that, or can you hold it there with the throttle?

If you can hold the car at idle with the throttle, than I would suspect a dirty throttle body/IAC or dead/malfunctioning IAC. I would clean the throttle body/IAC and go through the base idle reset procedure (this will require some special tools, you can get them from a corvette supply house - corvette central, Mid America, etc).

If the car dies well above 650RPM, then you have a different problem, perhaps a vacuum leak, or spark issue.


The FIRST logical step is to clean the idle ports in the TB and do the full idle set procedure (search in the tech section). It isn't difficult at all. I don't know of any special tools for this though.

Post the results after you do that
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