kevm14

I am going to be replacing the EGR valve on my 95 Z28 soon and I had a couple questions on this. First, is it generally advantageous to replace the control solenoid when doing the valve? Car's got 145k on it. I have no codes and no reason to believe it is malfunctioning. Second, should I attempt to clean the back of the intake out with, say, B12 Chemtool when the EGR is off? I've heard it can get pretty carboned up back there. Or should I simply remove the old and attach the new?

I wanted to add that I've been trying to track down the under 2000rpm hesitation/stumble thing. Yesterday I disabled EGR and closed loop in the PCM and I swear it drove very smoothly and I had trouble generating any kind of stumble or hesitation, even with the A/C on. Since the O2s are supposed to be AC Delco with like 20k on them, I figured I'd go for the EGR first, hence the above question.

kevm14

Nobody has an opinion on whether I should replace the solenoid?

I ordered a new EGR from GM Parts Direct without a solenoid so we'll see how that goes.

kevm14

Update: I received my new GM EGR from GM Parts Direct this afternoon. So at 5pm, I headed outside to attempt replacing it, expecting a PITA due to the cowl. Well, at 5:25pm, I had all my tools put away (I used a craftsman 1/2 inch wrench, the closed end, and I bent the solenoid down on its bracket for better access to the driver's side nut), closed the hood, and the car was running with the new EGR valve installed. And that includes running across the street for carb cleaner (I sprayed in the EGR passages). Hell, this was easier than on my 93 Caprice. Here is what the old valve looked like:

http://kmoore.phzero.net:8081/pictures/Camaro/EGR-1.jpg
http://kmoore.phzero.net:8081/pictures/Camaro/EGR-2.jpg

I will update again with any drivability improvements (if any).

944v8inDFW

little crusty there dood. Anyway at that kind of mileage it is time for a new one i am sure.

Ryan's LT1

Definately keep us updated, I have a mild stutter in my car at under 2000 RPM's as well.

kevm14

Did a little road test tonight. There is still a stutter but I may have improved matters. That valve did have 145k on it.
The previous owner of this car had a stutter/shudder that turned into a major drivability issue under load. It turned out to be the intake leaking oil onto the opti and #2 plug wire (maybe others). He had a chevy dealer do the intake gasket, plugs, wires and opti. He also had new AC Delco O2s put in at an independent shop. This was about 20k ago. Can I assume all of these parts that were replaced are still good? Coil is original...would the wires that a chevy dealer installs come with a coil to opti wire?
I was going to try the water spritz test in the dark to check for arcing, but to really test it, I'd have to put the engine under load. That's not really possible.
So should I get a coil to opti wire? How about a new coil?

I am really anxious to solve this.

Ryan's LT1, try cleaning your MAF (use q-tips, electrical contact cleaner or carb cleaner if you're brave like me, and a controlled but firm touch) and putting the screen back in. Do you have access to PCM flashing equipment? If so, try a flash where closed loop and EGR are both disabled (raise the min thresholds and lower the max thresholds where appropriate) and let me know your results.

Ryan's LT1

I have not cleaned the MAF, but I have put the screens back on a long time ago and forgot to update my sig. I'll do that in a second. I have fully cleaned my throttle body with carb cleaner, I cleaned the IAC valve and the TPS sensor. I also checked every one of my plugs and wires and they were all good. The problem has since gone away, but alas, a newer one has arrived. It idles pretty rough, you can kind of feel it buck, but not the kind of buck where it wants to push forward- it idles fine, and does not stutter any more. There's no more hesitation under 2k RPM, only the odd idle. And I'm thinking it might be the EGR valve.

I don't have access to PCM flashing equipment, or I would try that. I will however try cleaning the MAF and see what that does. I'll keep you updated. Any recomendations on what kind of contact cleaner I should use?

Thanks.

kevm14

To what do you attribute your fixed under-2000rpm stumble?
I agree, the EGR could very well be causing the odd idle. For electrical contact cleaner, I just went to Home Depot. There were 2 or 3 different cans and I just picked one. I did find that it wasn't a strong enough solvent for the caked on crap on my MAF wires. That's when I broke out my B12 chemtool carb cleaner. I also had to apply a fair amount of pressure with the q-tips to get all the stuff off.

This is a pic of the MAF where the upper two wires have been cleaned, but the lower three have not:
http://kmoore.phzero.net:8081/digita...0/DSC04126.JPG

The lower three were a little nastier than the upper two:
http://kmoore.phzero.net:8081/digita...0/DSC04128.JPG

Results:
http://kmoore.phzero.net:8081/digita...0/DSC04131.JPG

My car has always had a paper filter with all stock intake plumbing, and the MAF was still this dirty after 145k. Those with oiled air filters should pay even closer attention to their MAF wires.

Ryan's LT1

I would probably have to say that the IAC valve cleaning made the biggest difference, but it was probably a combination of all of them that did it. I had the biggest stumble off of Idle though, that went completely away by 2000 RPM's, so thats why I think the IAC was the culprit. I'm going to clean and re-charge my K&N filter and I'll clean off the MAF with some carb cleaner I have laying around. Those pics are good too, mine look just as nasty as those do, and my MAF is only a year old. I'll definately make sure I don't use too much oil on the filter and make sure it is very dry too before I put it back in. Thanks for the advice.