I've been trying to diagnose a little problem I've been having lately. Under light throttle the car seems to stumble/hesitate. If I take off from a dead stop it will feel like crap up until about 2k, then it will even out and drive fine (until the next stoplight). So my thinking led me to believe that I might have an EGR valve that was stuck open and was choking out the engine at low RPM. I diagnosed the EGR solenoid and valve today, and determined that the EGR valve is bad. The solenoid was supplying vacuum to the valve under part throttle, but the valve would not hold vacuum (tested with a vacuum pump). Having the valve check out bad just made it more confusing, because I'm thinking that if the diaphragm is bad, then it would not be opening when the computer commands it, and could not be causing my part throttle hesitation. However, when I disconnected the EGR vacuum line, it seemed to fix the initial hesitation problem. So, cutting to the chase: will a bad EGR valve cause a low rpm hesitation like I described? Either way I'm going to replace the valve, but in the meantime my curiosity is getting the best of me and I wanted to know what the Savants de Thirdgen think.

 

Some of those egr valves have a tiny port that senses exhaust back pressure & they wont open unless they sense it.
I'd disable the egr by unhooking & plugging the vacuum hose, test drive it
& see if the problem is still there.
The throttle postion sensor might be going bad, check fuel press. too.

 

Sure it can cause that issue! Some EGR will not hold vacuum like the old days so that is not a sure fire way to test them anymore.

Code 32 usually sets if there is failure of EGR system. Other times it just fails the test because results didn't meet quilfiers in test.

There's many threads her on code 32 to read but one I did with pictures and discriptions of the differant EGR valves and a weird story of a guy who got Code 32 after installing duel exhaust. Since it had a crossover he plugged one side of exhaust and no more code 32. unplugged exhaust and got code 32 back.
http://www.gearhead-efi.com/Fuel-Inj...BI-EGR-code-32

There's also a fe pdf from GM service manuals for TBI, TPI and V6 that show exactly how to diagnose each error code. A must have for DIY your own error codes and understanding how each circut works. Bottom of first post:
http://www.gearhead-efi.com/Fuel-Inj...-CEL-SES-Light

Here's another thread with code 32 information a couple forums up...
https://www.thirdgen.org/forums/dfi-...ml#post5172398

To get off EGR subject your problem may be TPS sensor starting to fail, they will go intermittent. Can be tested by watching voltage as you open throttle. Testing procedure is in the pdf above. HTH!

 

Thanks for all the info guys. The TPS was the first thing I tested, and it checked out ok. I unplugged the vacuum line going from the solenoid to the EGR valve, and it did seem to fix the hesitation. If testing the valve with a vacuum pump is not a surefire way to diagnose it, then what is a better way? I have the GM service manual so I'm going to pull it out and follow the diagnosing procedure for code 32 and see if I can find anything in there.

 

I just read through the service procedure for code 32 in the service manual. It says to test the EGR valve with a vacuum pump, and that it should hold vacuum and take about 20 seconds to bleed down. When I tested mine it would not hold vacuum for any amount of time, so it definitely needs to be replaced. Even though the problem seemed to be fixed with the valve disabled, I'm still confused as to why it would cause this to happen? My thinking was that if the diaphragm was broken and the valve was not opening, no exhaust gas would be getting into the intake and it would drive basically the same way as when it was disconnected. Obviously that is not the case.

 

Is the EGR solenoid valve working properly? If it is leaking it would cause the valve to open when it wasn't suppose to. If the valve diaphragm was bad you might throw a code depending on how bad the leak is but it wouldnt be causing it to open when it wasn't suppose to.

 

I tested the solenoid by taking off the hose going from the solenoid to the valve, and with the engine running and at idle it had no vacuum. Then I gave it a little throttle and the vacuum would start pulling through the line. I also put a vacuum pump on the EGR valve with the engine running and it still would not move (I can here the air being pulled through the diaphragm. So I'm pretty sure the solenoid is good. The problem still seems to be that the valve won't open at all because it has a substantial leak. Even if the solenoid was malfunctioning and trying to open the valve at the wrong time, it wouldn't matter because no matter what the valve won't move with vacuum supplied. So the main thing is that the valve won't open at all, and that's what I'm wondering about. Could the valve not being open when it's supposed to be cause the car to hesitate under light throttle? Or could I be experiencing an intermittent TPS problem, and the EGR valve/code 32 be unrelated?

 

Replace the valve....they are cheap. Test the tps with a sweeping arm volt meter, the needle should move very steady as the throttle is opened and closed.

 

Like I stated before, I already tested the TPS and it checked out fine. I also am planning to replace the EGR valve, so at this point it is not a question of "will this fix my problem" but rather a question of curiosity on the theory of EGR operation on our cars. I was under the impression that the car would not stumble if the EGR DIDN'T open, and it would stumble if the EGR opened too much or at a time it wasn't supposed to be (i.e. the valve was stuck open due to carbon buildup). Thanks for your reply though.

 

i just replaced mine today and it made a world of a difference, took a little while b/c the right fuel line and the IAC was in the way. i'm debating if i should replace the EGR Solenoid for the hell of it, it's like a $35 part.

 

Sometimes engine vacuum has a much more steady pull then a hand vacuum pump.

 

I would replace the solenoid and egr as a set. If one gets worn out the other one can't be far behind. The solenoids are by far cheaper than the valve. I bought mine at advance auto for less than 20. I use to have a neon and when you bought an egr valve it came with the solenoid as a set.

 

What did you spend on the valve? The cheapest one I could find was through RockAuto for around $55. I'll probably wind up replacing both as well. After 20 years, it's just a matter of time before it goes out.

I'm still not getting the answer to the real reason I started this thread, which more than likely is because I'm not doing a good job of relaying my question.

So we have established that the valve is bad. Disconnecting it solves the hesitation problem, but I want to know WHY? It obviously has to do with the valve not opening when it should. Is the computer pulling timing because it does not sense a drop in manifold pressure? Or is it because of some other reason? Again, all I'm trying to do is get a better understanding of the EGR operation, and more particularly, the ECM involvment in controlling the timing/parameters when the EGR is commanded. Does that make sense?

BTW, I started this thread on Saturday night when I had a few too many in me, so I'm sure that my first post was a little off from what I actually was trying to get at.

 

yea my egr valve was about the same, $55-$60 at autozone.

idk if i can answer your question. all i know is my egr got so bad that when i would first start up the car i could clearly hear the loud vacuum it was trying to pull for several minutes+ and after i got the old one out to compare it to the new it was obvious. but i just replaced it yesterday so i won't know if thats my only problem until i drive it a while.

 

Braves, Did you plug the egr line when you un hooked it and it ran better? If your diaphragm in your valve it leaking and your solenoid trys to open the valve it will create a vacuum leak (a small one). You also have to think if the computer thinks the valve is open it should lean out the mixture since you are adding inert air (exhaust) but instead you are adding o2 rich air (through your vacuum leak) you are leaning it out even more. That might not be whats happening in your case but it is a logical assumption, but we all know what happens when you assume.

Also for an egr look at advance auto. They have some real good coupons on the net and if you drop over 75 it is free shipping.

 

When the EGR valve is commanded to open by ECM the ECM also changes fueling and timing. So if the valve does not open and let in some exhaust, then fueling and timing are wrong...

Also if it is just a bad diapram when the solinoid is triggered to let vacuum open it, it's just a big vacuum leak. Double whammy.

You should plug that hose when disconnected and drive to see if the problem goes away? Also when disconnected if you do a highway cruise over 50 flat road cruise set or keep throttle steady it should set a code 32.

I wanted to help when you were asking but since I learned of all the differant EGR valves, and read one that tested would not hold vacuum? Some do? So I did not have clear cut answer and was waiting for someone who knows this exact car and EGR to answer.

 

That makes perfect sense. I wasn't considering that when the diaphragm is ripped that it would create a vacuum leak. I smacked myself in the head after I read nickfrmtx89's, seafarer12's and your response. That's what I get for never thinking outside the box. Thanks a lot to everyone that posted on here. Everything that everyone said definitely helped me out, I was just getting frustrated with myself because I just couldn't quite put into words what I really wanted to ask. Oh well, in the end it all makes sense, it just took a little while to get there. Thanks again. I'll post up again after I replace the valve and solenoid just for future reference.

 

i need to check mine, my ses light comes on only after driving down the interstate a bit, i havent pulled it yet but from what i described i was told its most likely the egr

 

Hopefully it's an easy fix. Is it just throwing the light on or is there a driveability problem as well?

 

no driveability problems, if im just driving around town it never comes on but as soon as i hit the highway and im goin over about 55 for a few minutes it comes on. There's no drop in performance and it goes away whenever i restart the car.

 

Something like that could be different things. It could be egr, solenoid, I have also seen map sensors give similar problems. Sometimes on an old engine it could just get plugged with carbon and give you an egr code.

 

im having the same problem also. i appreciate the comments, but i would like to know will this cause the car to cut off

 

yes, it would cause the car to cut off. on mine, sometimes it would cut off right after starting, sometimes it would run perfect for several minutes and then the RPM's would go crazy, i would have to keep my foot on the accelerator so it wouldn't die in traffic.

 

What did u do to fix the problem

 

replaced the EGR & IAC valve. and i've bought the part but i still need to replace the egr solenoid.

 

I just went through the same thing chasing qhosts for 3 weeks. Exact same problems you were having, replaced cap , rotor, wires, plugs, pcv, tbi gaskets, O2, vac lines and in the end it was the egr valve. It's still not perfect but hopfully it will pass emissions now.