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This one stunned me and my mechanic. Have 1990 Cam RS. I replaced EGR valve due to code yet I replaced it with generic part which was stamped pos. yet I knew the system is under neg. Guy assured me to use it. I did and ran my emission test. Failed.The GM dealer mechanic assumed I installed wrong valve and replaced with GM valve exactly like one I took off. The emission test was even worse in NOx and VOC. How can a GM part be worse than the generic? Any ideas.
and should I switch back? Still have GM one on now Anne
 

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Ice,
Are you certain that the egr is causing the problem ???? Just because the "code" points to the egr valve, it does not mean that that is really the problem. There could be many other factors involved. You need to find a good shop with the experience to properly determine what is actually causing the problem. It will save you money in the long run, the newer cars can cost a bunch when you just start throwing parts at them without knowing what is really the problem.
Hope this helps,

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Bill Koustenis
Advanced Automotive Machine
Waldorf Md
 

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Discussion Starter #3
I understand. I am very mechanical, have always done my own work. My point was, how could the GM egr valve NEG show higher emissions than the generic which said POS.? The time frame here for the two tests was 1 hr only.
And the first original egr valve I believe was toast as when I took it off I had all my weight on it to get the diaphram to budge, I believe it was sticking. All the codes have gone since I changed it and my engine knocks are gone and its running 200% smoother.??
Thanks for the reply
 

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The codes are gone, but it still fails the emissions test? Tells me the catalytic converter might be going bad. Or the AIR system has a problem.
You about have to put it on a scan tool to see what all the sensors are telling the computer.
Gotta be something simple. Don't know why a GM part would be worse than a generic.

One of the Chevy Performance mags did a test on performance catalytic converters, and none of them was anywhere near as low as a new GM converter.
 
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