EGR Valve???
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Laughing Gas
Joined: Jul 2001
Posts: 849
Likes: 14
From: Fayetteville, NC
EGR Valve???
Hi all...Got a question for ya's. I have a '78 351M completely stock. The last owner disconnected the vacuum line to the EGR valve and to the top to theair cleaner and all. With it like this the truck idles fine at about 600-700rpm like it should. When I connect the EGR valve to a vacuum source the truck wants to die and tries to idle around 200 rpm. Sounds like a V8 running on 1 cylinder. Any clues as to why hooking the EGR valve back up does this?
Moderator
Joined: Jan 2001
Posts: 56,976
Likes: 2,733
From: Virginia
EGR Valve???
I hope you are hooking the egr up properly. It does not go to a manifold vacuum source. It usually goes to a ported vacuum source from the carb, so there is no vacuum to the valve at idle. Also, along the way, the vacuum line usually passes through a thermostatic vacuum switch mounted in a coolant passage somewhere, that does not let the egr work at all till the engine is at least approx 100F.
