You can have excessive carbon build up in your EGR despite a good vacuum line from the component. There should be no or very little vacuum on the valve at idle. You need a vacuum gauge and run the self test to see if the vacuum vent valve is operating properly. The way to clean the passages is to remove the throttle body and clean with solvent and a brush. You can do it with various cleaners. a carburetor cleaner can do the job.
Hi There G!
This is a great question you are asking. So, everyone who is reading this also understands, when the EGR (Exhaust Gas Recirculation)valve has vacuum applied to the valve diaphragm, it pulls the valve open and allows the exhaust to pass from the exhaust manifold into the intake manifold. This dilutes the incoming air/fuel mixture and has a great effect on the combustion temperatures. Simply put, the EGR keeps NOX (bad emissions) within a safe range to go into our atmosphere.
I love this question, because I can see why you are asking. This EGR valve can go bad for a few reasons. It can become clogged with carbon that cause it to stick OR prevent it from closing properly. In your case, vacuum will open it. The best thing to do when your EGR valve is dirty is to replace it.
Be safe driving, Thanks for writing.
〉 Answered on May 7th, 2010 by Audra Fordin, Owner at Great Bear Auto Shop
Yes it can
〉 Answered on May 6th, 2010 by Barb Petrey, President - DBK Enterprises Inc at Jiffy Lube
Hello G-In a word*Yes. Several things may occur. Because exhaust flows through it, deposits may form which restrict or cut off the flow. Also, there is a spring above a diaphragm which closes the valve when vacuum is low or nonexistent. The spring will eventually fatigue allowing the valve to stay open when it should not. In addition, they have been known to occasionally stick open, causing rough idle or stalling. The passages can be cleaned out should they become clogged, but it is best simply to replace it. Hope this helps*Super Girls Auto.
〉 Answered on May 6th, 2010 by Laurie Sarno, Co-Owner at Super Girls Auto