If my engine revs slightly before turning off when the key is turned off does that mean the engine stop solenoid may be on its way out?

try the stop lever manually... same behavior?

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Cheers!
Scott McPhee

1987 300D

Does it rev AFTER you turn the key, then stop? Or like, you put it in park, and it revs up a bit right before you turn off the key?

It revs after i turn the key, then it stops.

just replaced mine half hour ago....disconnect the vacuum line and attach a hand held vacuum pump to shut off side. When you pump, the lever should go down, and stay down. It'll probably take a few pumps for it to go all the way down. If it comes up, the diaphram has a leak in it(assuming your hose connections are tight).

I suspect the idle control circuit is doing something to bump the idle during the shutdown.

If you disconnect the idle control on the back of the IP (two-pin connector), the idle will drop to about 550 RPM, which is the mechanical setting. If the behavior goes away, the problem is in that idle control circuit.

I have disconnected mine years ago, and increase the mechanical idle speed setting to about 750 RPM. The only thing I've really lost is the increased idle speed when the AC compressor is engaged. Somehow I survive...

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC