Quote:
Originally Posted by 97 SL320
A leaking diaphragm ( where the small vacuum hoses attaches ) would prevent the EGR from opening / opening fully depending on how large the leak is. However, it is never supposed to be open at idle so it's affect on idle will be zero.
Now, in the 80's GM used a EGR valve that looked at exhaust back pressure ( engine load ) and modulated the valve. This type of valve " probably " bleeds control vacuum to air when controlling EGR flow but it has been years since I've looked at this system. I have no idea if MB used this type of system.
A leaking pintle shaft seal is just like and other intake manifold vacuum leak.
You still have not described what constitutes a " strange idle ". ( Nor have you described the ruckus. . . )
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Thanks for the info.
And sorry meant to describe the idle earlier, just spaced. Car is idling high (~1400 P/N; 900 D) intermittently with no clear trigger for the idle. Some times it is fine sometimes it is not. Sometimes its fine when I start and for most of a trip, then its acting strange when I pull up to my destination. The cruise control also cuts out during the high idle. Car is running fine though even when idling high.
It could be the ETA, which is out for testing right now. I wanted to rule out vac leaks which is how I got to testing the EGR operation after my smoke test.