egr?

lowflying90

Registered User
can an egr valve go bad? if so, what are the symptoms of a bad egr?

at idle the tack will jump from 700 to 900 when it is missing. when i give gas, the wheels kinda lock up and the car stumbles. the miss doesn't happen all of the time. i just swapped my dis with the dis on my other car and that didn't fix the problem.

it doesn't do this all the time, it will run fine for a week then it will start to act up with these same systems, after a while it will quit and run normal.

it kinda makes a thumping noise back behind the throttle body that kinda sounds like "bass" from a subwoofer.

any ideas?

thanks
jeff
 
The EGR definitely can go bad. I had to replace mine.

I copied this off of the board a while ago(hope it helps):



As you may know a malfunctioning EGR system can cause poor idle, poor fuel economy, and
many other problems. As you also might know, the EGR valve on a SC is nearly impossible to
get to. At the very least it is extremely frustrating to try and remove it to clean or replace just to
"check" that it is OK. Here is a relatively simple test for the EGR system if you think there might
be a problem.

First up make sure your car has EGR, since not all SC's came with it. (can anyone help with the
years here? I know 1989 and 1994/1995 have it, but 1991 and 1992 don't...)

If you have EGR, you will need some 1/8" vacuum tubing to test the valve. Find the vacuum
fitting on the top of the EGR valve. The EGR valve is located on the backside of the plenum
between the throttle body, and the supercharger, it is hidden below the cowl.

Pull off the factory vacuum tube and put on your own.

Start the car.

With the engine idling, apply vacuum to the tube you put on the valve, this should open the EGR
valve. With the EGR valve open the idle should drop and become rough, eventually stalling. If
this happens the egr valve is opening OK.

Release vacuum. This should allow the engine to return to a normal idle. If the idle improves
immediately with release of the vacuum, the EGR valve is closing properly. I would open and
close the valve a few times this way to be sure it is not sticking.

You may want to also apply a partial vacuum, just enough to affect idle, but not enough to stall
the engine. Try to hold this vacuum to make sure the diaphram is not leaking.

Now if you know the EGR valve is functioning OK, you may want to check the EGR control,
this is the other half of the story. you will need to connect a vacuum gauge to the line that went to
the top of the EGR valve. This line should show no vacuum at idle, but should show vacuum
with a wing of the throttle.

If that is all happening, the EGR system is working properly, and you can reconnect the vacuum
line, and look elsewhere for the trouble, thus saving the knuckle scraping job of removing the
valve.
 
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