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Egr valve problem?

i have a 1987 Buick custom 3.8L that will not run or start with the EGR valve connected to the evr selenoid. how can i verify if it is the EGR valve or the vacuum selenoid? When I connect the egr to the vacuum selenoid the valve opens all the way up and the engine stalls.

If disconnecting the solenoid eliminates the problem then it has to be the solenoid. If it was the valve itself sticking open then disconnecting the solenoid wouldn’t help.

I don’t know the specifics of the system on this car but I assume that the EGR is vacuum actuated and it is the solenoid that applies the vacuum. If that’s the case then you can easily put a vacuum gauge on the vacuum line form the solenoid to the EGR. At idle you should get approximately zero inches of vacuum.

What’s left, however, is to find out whether or not there is a power issue - i.e. maybe the solenoid is fine but it is being energized when it shouldn’t be. For that you’ll want to back probe the connector for the solenoid. Its probably not supposed to get any voltage at idle. It gets voltage to actuate & open the EGR. Although, it could be the reverse of that - there are generally two types of EVR solenoids. One is normally closed & opens to supply vacuum when voltage is supplied. The other is normally open and needs voltage to stay closed. It may be that yours needs power to stay closed and has lost its power supply. Autozone’s free online repair info might have the testing procedure.

thanks for the info. here is some of the otheer things I noticed about the selenoid. I am not feeling any vacuum on the egr side of the selenoid if I put my fnger over the fitting, but when i pt the vacuum line on from the egr valve i can see the rod that goes into the engine start going up into the egr valve. I assume that is because of the vacuum sucking it up. Why do i not feel the vacuum when I cover the egr side of the selenoid?

As I said, I don’t know the specifics of the system, but it probably maxes out at all of 8-10in of vacuum. It could take as little as 3-4 to open the EGR enough to stall it. That’s not much so if you want to know whether its there or not you’re better off with a gauge.

Come to think of it, you may want to a gauge anyway. If the EGR valve’s spring is shot its conceivable that only an inch or two of vacuum could open it up enough to stall the engine. Its a 1987. I wouldn’t be surprised if you need both a new EGR & a new solenoid - i.e. the old solenoid bleeds a little too much vacuum through + the EGR valve spring is weak = stalling the car.

You best bet is to have a little hand held vacuum pump/gauge with which you could figure the whole thing out.

If disconnecting the EGR valve does not result in you failing an emissions test, then you can just leave it disconnected without hurting anything…

That’s not necessarily true. The EGR allows exhaust in & cools the combustion chambers. If you disable yours you can end up with pinging which isn’t a sure death sentence but will create damage over time.