QuestionI have a 1994 Pontiac Grand Prix,2door, 3.1 liter engine.About 3 months ago, my check engine light began to come on. Since and before then, I`ve had my transmission serviced, oil changed regularly, so I don`t think there is a problem with that. I went to a shop and had my car put on the computer and they said it was my egr valve going out and making my check engine light come on. They then stated if they fixed it they would have to put it on the computer again, at my cost, to make sure that was what the problem was. This made me think, and so now I ask anyone out there----DO YOU KNOW WHAT`S GOING ON? IS THIS A BIG PROBLEM?
AnswerTechnically is the EGR system not working a problem... not really... not as long as your car runs just like it did before.
Basically, mechanics will always go with the easy fix, being the EGR valve if you have the EGR code in the computer.
BUT... and the BIG BUT, is that if you read in the service manual it says... replacing the EGR valve may NOT solve the problem and relieve the service engine soon condition.
What happens is that if there is a VACUUM leak in a hose anywhere from the EGR valve to the EGR solenoid that could cause the code. Also, the EGR solenoid could be bad. It is the valve which regulates how much vacuum gets to the EGR valve itself, basically it controls how much the EGR valve opens.
In one of my cars case, the EGR solenoid was bad, but the code would only come on when I cruise for extended periods of time at the same throttle, lets say one minute. I did not want to pay a whopping 80 dollars for a measly little EGR solenoid so I just put up with the light whenever I'm on long traveling.
If you speak to a mechanic they will tell you it's imperative that the EGR system work correctly, becuase in some cases it can cause knocking and pinging and some other sorts of problems, but in most cases it makes no difference. I've known people to run tens of thousands of miles without the EGR system working and their cars work just fine, my Fiero included. It has run over 40,000 miles with the sytem inoperational and at 126,000 miles on the original engine it still runs great. Just a tidbit of info.
The real reasons I have left it inoperational is because the 80 dollar solenoid, and the fact that Fieros have a notorious problem with the hose that goes from the EGR valve to the INTAKE plenum. IT CRACKS and sucks in additional air and then give you a HIGH IDLE condition. That's not good, I've changed the hose twice in 4 years and this last time I just plugged everything and didn't get another one.
I hope this clears up any confusion.
By the way, you should tell them to TEST the EGR VALVE first. If you have a vacuum pump, or they I should say is to apply vacuum to the valve, if the valve opens and stays open, then the valve is good. But if it opens and then loses vacuum, or simply just does not open at all as vacuum is applied, the valve is bad. It should be checked first to VERIFY that that is the problem. If that is not it, then their could be a broken or leaky vacuum hose or an inoperational EGR solenoid. The vacuum piping can be tested the same way with a vacuum pump. Basically the piping can be tested by testing the valve THROUGH the piping by disconnecting the piping at the EGR solenoid, only after testing the valve to make sure you don't misdiagnose.
If both the tubing and the EGR valve are OK then the solenoid is bad. Don't let them take your for a bad ride, make sure they test the valve and the tubing first.
I know I put out a lot of information, but I'm just trying to explain it as simply as I can with everything you need to know to KNOW what you are talking about.
