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Old 06-15-2003, 04:20 PM
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moparmike moparmike is offline
You will rue this day...
Join Date: May 2003
Location: NW Arkansas
Posts: 732
Originally posted by psfred
Sounds like a vacuum leak. Does it shift hard too?
Nope, no hard shifting. Well, it does to reverse, but I'm sure thats an entirely different ordeal.

The climate control PBU is a sore point these days -- my parts guy got three bad ones in a row, one brand new. Didn't make him very happy, believe me!
Sorry to hear that. Hope mine turns out better. MB is a good company, and it shoud fix something when it turns out to be crap.


Check for hard or broken rubber hoses in the engine compartment, especially on the idle control valve. If leaking, dirt gets into both the engine (very bad) and the idle valve, making it stick -- it goes closed to slow the car, then won't open fast enough when you stop. Most often stalls after an abrupt stop when this is the case. Can be cleaned, but you wil need to replace the rubber hoses, probably all of them.
Where might the ICV be on a W126?

If you get rough idle ONLY when the brakes are applied, you have a bad brake booster that causes a major vac leak when the brakes are applied only. Happened to me in Canada in the old Dodge Aries. Caught on when I heard a hiss only when I had my foot on the brake.

If it isn't a vac leak, I'm over my head.

Its not really a rough idle, just rpm's bottoming out.

I should have posted this in the first one. When I brake, the rpms go to near zero. It has sometimes died and kicked back on from centrifugal inertia of the internals (i would assume). When it does die, the same thing happens. I have tried to stop this by shifting into neutral, but its like someone hits a kill switch and it goes from 1500rpm to 0rpm instantly.

Thank you for your reply. I encourage any other suggestions anyone might have.
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