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Old 01-27-2007, 12:12 PM
Registered User
Join Date: Jan 2003
Posts: 13
Unhappy 93' 190E 2.3L hesitation/stumbling

I purchased this 1993 2.3L car 123K miles. Here are the conditions:

When first started and cold the idle is great very little or no stumble on take off. If driven on the freeway (warm to hot) then the idle will start to wander (good a few seconds then drops for a second) when you city drive at stop signs (like a miss and giving throttle at idle doesn’t always correct it)(sometimes it idles just fine and only has the stumble on take off?)

Once warmed the hesitation/stumbling usually gets a little worse off the line. Never stalls but acts like a miss and misses more when you first take off hard again (still in that 1000-1500rpm range.) Afetr 2000rpm it drives well and always cruises great at any speed.

Occasionally when under full throttle on a down shift the engine seems to go flat around 4000rpm and just hangs in 3rd gear until you let up the throttle and it up shifts to 4th and you have power again. That seems to be better since the vacuum lines were replaced to and from the idle speed seloniod.

Any ideas for this vintage CIS Mercedes? Thanks

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Old 01-27-2007, 12:20 PM
JamesDean's Avatar
Electrical Engineer
Join Date: Apr 2005
Location: NE Ohio
Posts: 5,034
might i suggest looking for additional vacuum leaks? I had some stumbling idle troubles (mostly when i was at a red light) and I discovered that I had inadvertently disconnected a vacuum line at the EGR and not plugged it up. Check into your system and see if there any leaks. i've heard that the m103s dont like them at all, I dont imagine the m102s like them anymore

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Old 01-27-2007, 02:23 PM
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Join Date: Jan 2003
Posts: 13
I agree - continue looking for vacuum leaks. The vacuum bounce at 15-16" at idle and drops to 13-14" when put into gear (measured at ignition control vacuum port with tee connection). Anyone know what is common to these cars for leaks? EGR replaced with leak. Transmission modulator checked. Rubber U shaped tubing under plastic intake box to idle speed seloniod replaced, rubber tubes from same seloniod to valve cover & air cleaner replaced.
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Old 01-27-2007, 06:59 PM
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Join Date: Jan 2003
Posts: 13
Well the vacuum was low due to the air fuel mixture being misadjusted. I had fixed all the leaks prior and was chasing ghosts. Adjusted the air sensor for peak vacuum at idle and got back to 20" at idle. Now I have a smooth idle. Still has a bit of stumble off the line but obviously not nearly as bad. Must be some thing else to get it to accelerate better from 1000 rpm to 1500rpm.m Maybe it is a simple as timing?

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