Probably the EGR works ok. I'll check diaphram operation later today. My concern is with intake air leaks.
My test may be inconclusive but an air leak around the EGR valve stem impacts idle operation directly since it provides UNMETERED air into the intake plenum. If it's very little then it can be compensated for with the idle adjustment on the Idle Air Adjustment (IAA) unit with virtually no impact on the a/f ratio. If it's a lot then then the MAF sensor senses too low a flow value at high vacuums around idle the engine will run lean. On a NA the proportion of such unmetered air drops off as the throttle is opened and plenum vacuum falls off. These are the symptoms my car is exhibiting but since the EGR valve seems not to be hermetically sealed by design the question is how much is too much? Help.
