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EGR valve

Our 1998 Toyota Avalon is driving me crazy! When we drive at highway speeds( 60+) for an extended time and then come to a stop the engine starts to flutter like it wants to stall. The first time it happened we took it in and tests showed a leak in the fuel vapor system. The gas cap was tightened and the computer was reset. It happened again and the mechanic checked for vacuum leaks but found none. He suggested a new fuel filter which we had changed. A month or so later and it’s doing it again. I checked with a Toyota shop and they say it could be the EGR valve. Does this make sense to change? Is there a test to show for sure it is the EGR valve failing or does it have to fail completely before we are sure? We are getting afraid to drive it on the highway in case it strands us somewhere. It never happens while driving around town only on the highway. What are your thoughts please?

Starting with a check for vacuum leaks and a new fuel filter wasn’t a bad idea. (But how are the air filter, spark plugs, wires ?) But it doesn’t make sense to change anything in the EGR system just based on a guess. They can be tested. Sometimes things can just be cleaned. You can check this out:
http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c1528009266a

It sounds like you’re at the point where you need someone to spend some time actually checking/testing things. A basic check of fuel pressure, ignition system, EGR system check would go in here too.

I would suggest dropping by a local chain auto parts store (AutoZone, etc) and have them pull the codes. They will do this for you free and it only takes a few minuts.
It’s possible a sticking EGR could cause this but it’s also possibly related to the Idle Air Valve circuit.

Once any codes are known then the diagnostic work starts.

It does make sense for a shot in the dark. It may be hard to just diagnose since it only happens after highway speeds. It could be related to the throttle body too.