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1991 190E 1.8 auto; 1992 180E 5 speed
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313 Posts
Discussion Starter #1 (Edited)
Hi guys,

I picked up a 1991 190E 1.8 with automatic transmission last week. (Engine is the M102 with Bosch KE Jetronic injection.)

After driving it around 200km during the last few days, I've just this morning discovered an issue. When I'm slowing down to a crawl or a complete stop, with my foot off the accelerator pedal (typically while braking), the engine starts to rev erratically as it drops back below about 1200rpm and speed slows below 20km/h. It revs up and down between 800-1300rpm for about four or five cycles, almost like it's trying to stop itself from stalling. In fact - the sensation is not unlike being in a manual car slowing to a standstill when the driver's forgotten to press the clutch, except the Benz is not actually stalling (well, so far not yet, touch wood).

I've found it happens with the transmission selector in R, D or 3 (haven't tried the selector in 2 yet but I'm assuming no difference there).

I've found that I can avoid the problem by holding down the accelerator pedal just a touch to prevent it from going back to idle, and then gently releasing it after we've come to a complete standstill in D. As you can guess, it's a bit tricky to do this while braking and trying to drive smoothly in traffic in general!

Note that the car has been a little bit hard to start (sometimes only starts on the second attempt) and is 2000km overdue for its 170000km/105000mi service, but otherwise in very good condition and running very well. From my extremely basic level of knowledge of things automotive, I feel like this problem may be slightly more involved than something like a dirty spark plug and and I shouldn't simply assume it'll be solved by the basic 170000km routine service.

I'd already booked the car in for its 170000km service with an approved Benz mechanic next week, but I'd be interested to know your thoughts on the cause, if for no other reason than to be able to make sure that the mechanic is also aware of it and can ensure it's fixed.
 

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Registered
1984 190D 2.2
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2,458 Posts
It could be something basic. If the service doesn't work, I would check out the stalling thread and see if anyting there helps.
 

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Registered
1991 190E 1.8 auto; 1992 180E 5 speed
Joined
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313 Posts
Discussion Starter #3 (Edited)
Hi guys,

Here's an update. The problem was traced to the air flow meter going open circuit and the electro hydraulic actuator valve (whatever that is) leaking fuel. I've been advised to replace these two parts, together with a "lever section" and another part number that googling suggests is a "mixture adjustment screw repair kit". I've also been recommended to clean the throttle butterfly and idle solenoid.

Mercedes Benz Australia has a parts list price of AUD$3677 (~US$3600) for the air flow meter alone! I'll probably try and source one from a wrecker/breaker's yard.
 

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Registered
1991 190E 1.8 auto; 1992 180E 5 speed
Joined
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313 Posts
Discussion Starter #4
erratic idle problemb appears to be solved

Just an update:

Got used a AFM unit installed for the princely sum of $500, the car now purrs like a kitten. Touch wood it's all smooth sailing from here.
 
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