88 2.0L Idle Problem

[GotToGo]

This summer when I was returning from a camping trip I had to stop on the highway for an accident. After sitting at idle for a few minutes I turned the engine off. When I started it back up (15-20 mins) it wouldn't idle. It ran fine off idle, but it would always die when I let it idle.

After driving for a while it began to idle ok and everything seemed fine. But an hour or so later when I hit the city, it started again when I pulled up to a light. When I got home I adjusted the idle up to keep it running but I discovered that the idle was surging high and low. It was the low that was causing it to die. It did this off and on for a couple of weeks, but now it does it all the time. I also discovered that it starts up and idles perfectly when it's cold, but as the temp comes up the surging begins and only gets worse.

It seems like a vacuum leak to me but I can't find one. I checked all the connections with brake cleaner including the carb and entire intake manifold. No leaks.

There are 2 thermo vacuum switches, that I can find, and disconnecting or bypassing them has no affect.

Any ideas?

[D50DAVE]

Did you check the egr, or pcv valves?

[GotToGo]

PCV seems fine, but I'll replace it anyway.

I don't know how to check the EGR.

[4doorciv]

Apply vac to it and see if it moves. I'd use a mighty vac but maybe you can apply engine vac while the car is running and you can hear the change in idle quality. It'll wanna die if you have the car running and apply the egr.

[D50DAVE]

There is also a chance it burned a valve. Don't replace anything until you rule everything out. Do a compression test.

[camoit]

Put a vacume guage on it. If the needle moves back and forth like a whip burnt or bad valve. If it's steady start looking for somthing like an EGR valve that is stuck open. Need more info. carb of FI. Did you block off the vac lines to the air clraner. Also check the dist. for bad bearings. It shouldn't move in and out. I would bet it's vacume related.

[GotToGo]

So I finally got the PCV replaced and there was no difference.

I pulled out my Haynes and looked up the EGR and followed its test procedure (feel for movement when the rpm is increased) and found there was no movement. So I'm guessing the EGR is stuck.

However, (there's always a however), My EGR doesn't match the one in the manual. The picture shows 2 ports on top while mine only has one. Could I be way off here?

[pennyman1]

Haynes manuals suck - they are very inaccurate for our trucks. Pull the EGR off and decarbon it and the passages. Use a hand vacuum source to make sure the EGR works after you're done

[GotToGo]

Yes, I'm still fighting this.

I was talking to a guy who apparently worked on these trucks in the past. He was telling me about an air valve in the exhaust pipe just below the manifold that opens and closes to supply warm air to the carb. He said this valve was a common failure on these engines and probably the cause of my idle problem.

So I looked at it and there "is" a mechanism coming off the exhaust pipe (not the one on the manifold that leads to the air intake) that feeds to a vacuum controlled valve at the top of the engine that feeds to the back side of the air cleaner. This vacuum valve seems to be working as I can feel and hear it shut off after the engines warms up. But he was talking about a valve down in the exhaust pipe. Is anyone familiar with this?

[4doorciv]

Do you have a picture of this?