Ok, here goes. The motor is a '89 LO3 w/ 67k. I have added true dual exhaust to it a while back and ever since have had a CEL on the highway. The exhaust has duals cats and mufflers. My egr valve is working properly.

The solenoid needs a few things like coolant temp, tps, ecm control etc in order to ground the solenoid and have vacuum enter the egr valve.

I'm assuming the problem is the lack of backpressure to the easier flowing exhaust. So i got to thinking and i installed a '96 LT1 Camaro EGR valve. It worked for one day and then i got the code again. Another valve i could try is the 96 Camaro 5-speed egr valve since it was made for an even lesser restrictive exhaust.

Anybody have anything to add? I'm kinda stuck and I can't really find an actual solution. Thanks,
Adam

 

I don't know what type of back pressure the LT1 EGR valve uses, but the 89 LO3 EGR valve uses negative back pressure if I remember correctly.

 

I was told by another guy that it uses positive and that i should try switching to a negative one.

 

I saw your other post and the gentleman is correct, you should be using a negative back pressure EGR valve. It is identified by the letter "N" in the P/N or the letter "N" stamped on it.

 

Ok, now when you say should be, do you mean stock or now that i have modified exhaust?

 

The negative back pressure EGR is what came on the stock engine, your modified exhaust may require a positive or ported EGR valve. I have little experience with a modified exhaust like yours, so I can not give you a definitive answer

 

No, i have a positive backpressure egr valve stock. He was suggesting using a negative one.

 

Okay,

My bad, I just noticed in your profile that you have a caprice. The information that I have been giving you is for a camaro, trans-am, or firebird.