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1990 Hardbody Pickup - Rough Idle

2.4L KA24E

Extremely rough idle (shaking, stalls when cold) but smooths out with higher RPMs, but occasional misses.

Changed fuel filter, plugs and wires. Distributor cap contacts are worn (will replace that plus the rotor).

Added iso-heet in case it was water in the tank. I use only Chevron fuel, but also added a few bottles of fuel injector cleaner. Went through another tank of fuel. No change.

For what it's worth, the ECCS computer reports no problems (I had to take out the seat to get to it!)

EGR valve diaphragm moves easily, but I'm not sure if it is being actuated though. I have not tested the solenoid controlling it. Can I connect straight battery power to test it?

AIV valve WAS stuck - freed the plunger and reassembled...I heard movement using a simple vacuum bulb after I put it back together. I did not try hooking battery power to the controlling solenoid, instead I hooked my DCV multimeter to the connector leads and only got about

1V. Should this be at 12V? Can I test the solenoid using straight battery power? I really have no idea if a malfunctioning AIV would cause this problem or not.

With so many possibilities, I'm just wondering where I should attack next.

Any help is appreciated.

Robert

Reply to
Robert
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ya know the dealer techs would just start replacing parts. by the way have you checked the timing?

Reply to
reddave1999

Timing is controlled by the ECCS computer on this one.

snipped-for-privacy@cs.comnospam (reddave1999) wrote in news: snipped-for-privacy@mb-m23.news.cs.com:

Reply to
Al

Well, the problem has disappeared.

After I "unstuck" the AIV valve, I had tried just starting it up and running it in the driveway, and the problem persisted. Tonight I took it out on the freeway for about 30 minutes. I revved it pretty good in a few stretches and by the time I exited to turn around, it was idling nice and smooth.

I'm glad it's working again, but I have a feeling this problem will return sometime. I wish I knew what it was. Hopefully I'll be on to a new truck by that time....

Reply to
Robert

Possibly a bad fuel injector?

Try pulling a plug lead while it's idling roughly and see if it gets worse. If it gets worse, plug it back in and move to the next plug. If it doesn't get worse for one of the plugs, that may be the bad injector, or it could indicate another problem related to that cylinder.

It worked for me in a similar situation.

Andrew snipped-for-privacy@hotmail.com

Reply to
Andrew

Reply to
N Todd Sides

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