Stupid EGR Question

[bigred88]

I'm trying to troubleshoot a surging idle issue on my friend's truck (1990 K1500, 350). I pulled his EGR, and cleaned it, and checked if it would move (it did), but the shaft doesn't extend out past the base. I included a link to an EGR below, if you look at the third picture on there you'll see what I'm talking about. On that picture, the shaft extends a solid 3/4" past the base. If it doesn't on his, especially after cleaning, does that mean it's stuck and needs replaced?

http://www.oreillyauto.com/site/c/d...=Search_02145_1050848_1386&pt=02145&ppt=C0018

My instincts say it's bad, I just wanted confirmation. I'm learning I don't like working on other people's stuff as much as mine- I don't get too bothered when I replace a part and it doesn't fix the problem as long as I had good reason to suspect it, but working on a friend's I really don't want to waste his money on parts he doesn't need. We already replaced the cap, rotor, and plug wires (which definitely were needed- lots of corrosion between the cap and coil wire), and they didn't fix the problem.

 

[British Slave]

The movable plunger is inside that part that sticks out.

 

[bigred88]

Ok. The underside on his, where it mounts to the intake, is completely flush (actually a little recessed in the same place where the piece sticks out on the new one). There is no part that sticks out- is that part not movable? Because I can push on the moveable plunger, which is the only part on there.

I wish I had taken a picture. Now I want to go home and take mine off for comparison. It's been a long time since I've taken an EGR off, and that was on an AMC I6. Never messed with one from a SBC before.

Thanks for the reply- actually, thanks for all of them today.

 

[British Slave]

I have an old one on my bench I looked at. The part you are talking about sticks out about 3/4" like you say. But the plunger inside it is all that moves. It appears theat piece you reference is screwed into the cast iron housing.

 

[bigred88]

Hmm... I wonder if there's any problem with not having that piece on there? I think I'm just going to recommend putting a new one on. If it was my truck I'd do it. What worries me though is wondering where that cap (or whatever it is) went? I mean, the only place for it to fall is into the engine. I'd think that would have been noticed by now though...

Thanks for looking!

 

[dyeager535]

Be careful with EGR's. Many are sold as "universal" and they are typically far from it. Enough problems that I'd be leery of replacing a stock EGR with anything but one from Delco with the same numbers stamped into it.

Probably overly conservative in that belief, but there are two completely different EGR's in terms of operation that GM used, and multitudes of different EGR's in physical construction.

 

[British Slave]

I'll throw out another question....Should the vacuum diaphram hold a vacuum when pulled with a hand pump?

 

[bigred88]

I've heard in the past that they're one product to not mess with aftermarket suppliers. I've got a pretty good local auto parts store around the corner from my house- I'll make sure we go to them and get a proper Delco part. Thanks for the heads up.

 

[dyeager535]

I'll throw out another question....Should the vacuum diaphram hold a vacuum when pulled with a hand pump?

I *assume* that's the case for all of the GM EGR's we might run into, I can't think of ever hearing of any that "bleed off" over time. All the EGR solenoids I can think of used a vent for when EGR was no longer commanded, leading me to believe they had to hold vacuum indefinitely, or at least within reason.

My setup is from a car, but I know the solenoid has a vent port on it.

 

[British Slave]

Yes, the solenoid is vented. The reason I asked, I replace the EGR on my truck a few months ago. Last week it suddenly started idling rough, die, lope like a big cam, but would run at cruising just fine. The first time I worked on it, I cleaned the EGR and it helped...for a couple of days, now it's back to the the rough idle. I put my hand vacuum pump on it and it wouldn't move. After cleaning the first time it would move with vacuum. I had another EGR on the bench off my new engine, and it too will not move with vacuum. The port on the diaphram is orifaced, with only about a.002 opening.
I did take the "extra" EGR apart. The thing sticking out is brass and is threaded, it is the seat for the plunger. That EGR was exactly like my original.
Working on a block off plate now. It's too much trouble and it's going to be gone. If need be I'll have a chip reprogramed to take the EGR out.

 

[bigred88]

You'll need a chip- at the very least, you'll get a pretty frequent check engine light. I'm not sure if it will cause any actual running issues. I've read a few posts about it, I just can't remember what exactly has been said.

 

[British Slave]

Here's a good thread:

http://coloradok5.com/forums/showthread.php?t=287181&highlight=egr+valve&page=2

 

[British Slave]

Update on my EGR issue. Got my block off plate done, and started to remove EGR this morning. This is what I found with the EGR:

Think I'll clean it and run it a little longer.

 

[4X4HIGH]

Do a search on my name and you'll eventually find a post that I explained exactly how to test both the EGR valve and the EGR solenoid. The post is probably a couple years old now and I can't remember if I started the post or just replied (pretty sure I just replied). The info came direct from AllData.

 

[British Slave]

After cleaning it, now the truck runs like it is supposed to. I am kinda worried about all that carbon. I may go ahead and remove the EGR, I don't want to deal with having to take it off and clean it.