My EGR Solenoid was bad. It was idling rough and had a hard time idling at all between 1200-1800 RPM. I finally diagnosed it down to the EGR Solenoid. The coil in the solenoid had an open in it so it was always open 100% of the time and the ECM couldn't change it.

After that I bypassed the EGR system and the car has been running ok.

So, I finally got my new EGR Solenoid from GM Parts Direct (replacement was exactly like my old one). Then I installed it. Now it passes all the EGR Diagnostic steps. At this point I was happy and then I drove it.

Well, now it hic-ups and bucks under light throttle. Its like what I had way back with the bad solenoid, but not as bad. At idle or heavy throttle its OK.

I checked for vacuum leaks with starter fluid and didn't find anything.

My muffler is leaking a bit, not terrible or anything, but I'm wondering if it could be low exhaust back pressure at the EGR?

To me, it seems like I'm getting too much EGR action.

I have never gotten any ECM codes. Not when the solenoid was bad. Not when the system was completely bypassed, and not now. I normally drive 2 hours on the highway each day too.

 

PCV is the other controlled vacuum leak. How is yours?

 

Time to check the EGR valve. It might be siezed on the shaft and stuck in that position. Did you replace it when you changed the solenoid???

 

- The PVC was recently replaced less than 2 months ago when I did a tune up.

- I didn't replace my EGR valve... When applying vaccum to the EGR the engine stumbles as expected. Its OK otherwise. So, its not stuck. Maybe weak though?

- With my EGR bypassed the car runs OK.

 

Follow <A HREF="https://www.thirdgen.org/techbb2/showthread.php?s=&threadid=249668">THIS</A> thread.

 

I replaced my intake manifold this past spring. When doing this job, my EGR Solenoid lines completely shattered beyond repair. I replaced them with new hard lines. I'm wondering if there is a possibility I could have swapped these lines around by mistake.

Could that explain it? If it somehow stressed the EGR Solenoid it could even explain why it burned out.

Does anyone know which EGR Solenoid nipple goes to the EGR the Metal one or the Plastic one?

 

I have the EXACT same problem with my 89.

 

Steve89GTA, please elaborate... Did you have EGR Issues, find out that our Solenoid was bad. Replace the solenoid and then still have problems??? Or do you mean, just the problem with the hard lines shattering???

I'm going to have to bypass my EGR again, because it drives awful. Also, I'm afraid, if my lines are mixed up, I might fry another Solenoid.

I'm not sure what to do here. I guess when I get a chance, I'll just have to try routing the hoses differently.

I do know (from driving around with a vacuum guage connected to the EGR port) that my Solenoid de-energizes the EGR under heavy throttle.

Also, the problem doesn't seem to happen when the car is first started. Meaning the ECM must be properly not enabling EGR when it is cold.

 

I've been having the same problem and I've been trying to solve it by burning a new chip, since I can't find anything mechanically wrong.

I've taken the EGR duty cycle down from 50% to %20 in the lower rpms and from 100% to 75% in the mid range. It helped, but I think I could go a little further because I notice some slight bucking at ~1800 rpm.

 

I have verified my vacuum hose routing. Metal solenoid port goes to throttle body ported nipple. The plastic solenoid port goes to the EGR. I believe this is correct, because I can hold a vacuum with the Ignition On on the ported side. The EGR side release to atmosphere in that mode. Bottom line being, I think my hose routing is correct.

The fact that I did not have this problem prior to my EGR Solenoid failing says my EGR is good. I have verified operation of my EGR Solenoid so that would indicate my EGR is bad.

AlexJH:
Have you ever replaced your egr solenoid or egr valve?

 

Kind of sounds like a vacuum leak somewhere. Retighten intake bolts, upper and lower. With a MAF system any air into the engine will lean it out as the MAF isn't measuring anything behind it. EGR base gasket cracked, TB gasket, air intake bellows, anything.

 

if you unplug the egr , will the car run ok or do i need to disable that in the chip

thanks

 

If you unplug the EGR it will throw a code until you disable that in the chip. (There's an EGR diagnostic checkbox you unclick.)

My EGR did the same thing a couple years ago, I shot 90 PSI of air into it with my compressor to force it shut, plugged off the solenoid vac lines, disabled it in the prom, backed off my timing a little... been golden ever since.