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  #1  
Old 02-14-2005, 10:42 PM
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Join Date: Dec 2004
Posts: 22
Idle Surge Issue

Searched & searched and haven't really found a definative answer to my specific issue so, here goes...

My '94 E320 Cabriolet has an idle surging problem; not a huge surge but enough to be obnoxious. When the car is in gear at an idle, the RPM will jump from 550 to about 750 for a moment or two. This also seems to happen in reverse. Can't say for sure that anything else is wrong but I think my shifting might be a tad rougher than it had been.

Have seen a lot of references to vacuumn leaks, to Idle Control Valves, to MAFs, etc. etc. in the persuit of fixing a rough idle. How do I narrow down the hunt?

BTW, new motor mounts about 3k ago

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Old 02-16-2005, 11:10 AM
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Join Date: Dec 2004
Posts: 22
Cab idle surge

Let me add:

The idle surge doesn't happen all the time, it's intermittent. Happens more-so when the car is cold (from sitting overnight in the garage). A mechanic said "It must be the Idle Control Module"; that's funny... is there such a thing on a '94 E320 Cabriolet?

Gimme any ideas guys!
Thanks in advance
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Old 02-16-2005, 05:49 PM
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Join Date: Sep 2003
Location: Dallas, Tx
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My car did that too, when in reverse and sometimes while sitting at a light, it was never a constant thing, and it would just happen. I have a 96 SL320, it turned out to be a bad purge valve, the idle control module would try to compensate for the vacuum loss and to do so it raised the idle. It was a messy gremlin to find and the CEL light would come on and go off, strange almost haunting, but vaccuum loss can effect idle and other things like when that darn electric pump kicks in that sounds like a vaccuum pump when cold, or I put my soft top down, this increases drag on the alternator and I can hear the idle go up.
Thanks,
Brian

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