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1988 GMC Van Repair Question

Topics covered: Gas, Idle air control valve, Mechanic.
Mileage: 145,000 miles.

Asked on November 27, 2011

What is the cause of my idling problem?

I have a 1988 GMC Vandura 2500 5.7 ltr V8. Here's my story: The van was slowly acting weird, strange idle, lack of power. I tried to leave a parking lot on Thanksgiving, and it just died and wouldn't start back up. I thought I had bad gas or something and had to get it towed. I put in Lucas gas treatment and put higher octane gas in it (about half a tank) and it seemed to be better. Now it's idling erratically again. Up real high then down real low and wants to die. back and forth, up and down. I have to give it gas to keep from dying when the idle drops. What could it be? I saw a section on here about a vacuum leak causing a whistling sound. I have noticed the past month of a whistle sound that was not there before. Please help me, I already had to be towed on Thanksgiving and I'm very poor right now.

Asked by Joshfahrenheit

Answer

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Replied on November 27, 2011

Clean out the idle air control valve and EGR/PCV valves and see what happens

Answered by rasmataz
68 questions asked

Replied on November 27, 2011

Okay, will do. I'm not much of a mechanic. I'm trying to find where the idle air control valve is located, not coming up with much online.

Response from Joshfahrenheit
1 question asked

Replied on November 27, 2011

Its on the throttle body-you need a repair manual

Answered by rasmataz
68 questions asked

Replied on November 28, 2011

I found it! Took it off and cleaned it with carb cleaner. The springs around it moved but the post (part with metal tip) didn't seem to move in and out. I'm not sure if it is supposed to or not. I put everything back together, and no real change in idle- still up and down. Onto the EGR/PCV valves i guess????

Response from Joshfahrenheit
1 question asked

Replied on November 28, 2011

When you turn key on the IACV should move if not its defective

Answered by rasmataz
68 questions asked

Replied on November 28, 2011

Okay.. I turned the key and could see the IACV move in and out. Pretty cool :) So we can rule that out?? I think I've located the EGR valve. Just remove it and clean? Thanks for all your help!!!

Response from Joshfahrenheit
1 question asked

Replied on November 28, 2011

You're welcomed

Answered by rasmataz
68 questions asked

Replied on November 29, 2011

One last question. The IACV did NOT move when the ignition key was in the "on" position. It only moves when I started the engine up. Is it defective?

Response from Joshfahrenheit
1 question asked

Replied on November 29, 2011

Go to this link and understand how it works-http://www.2carpros.com/articles/how-a-idle-air-control-valve-works

Answered by rasmataz
68 questions asked

Replied on November 30, 2011

Well, I changed out the IACV, seemed to do better, then it was bad again. I took out the EGR- it seemed stuck, so I sprayed wd-40 and had it working smoothly. Neither seemed to fix my problem. It got worse and worse and finally stalled wouldn't start up again at all. I had to have it towed to a mechanic :( Any thoughts on what it could be? I sure hope i don't get ripped off.

Response from Joshfahrenheit
1 question asked

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