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Discussion Starter #1
Hi, I have a 97 (pre facelift) C230 automatic which has a rough idle. Somethimes it even dies when i stop in a crossroad etc. However there is no real pattern to what causes this. Most often it happens when it is cold outside, but also after a car has ben parked for a short period of time (<1h) and engine is still hot. In idle when it is rough the motor shakes violently. However this is not something that would happen every time I drive a car. When I drive to work (30 min ride) it usually works perfectly.

I read it could be MAF, but I dont know since it is not happening regularly.

Thanks for help!
 

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2002 ML55 AMG, 2005 Chrysler Crossfire Coupe Limited, 1999 C280
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Please have the car scanned for OBDII codes.

That will give us the best clues as to where to start.

Is the 'check engine' warning light illuminated?
 

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Discussion Starter #3
There are no lights turned on. Judging by control lights everything is fine. Regarding OBDII codes my friend who is a mechanic did hook it up to a computer but said that nothing is showing - again as if everthing is OK. I am puzzled because this thing comes and goes. Maybe some sensor or something that has a bad connection...
 

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2002 ML55 AMG, 2005 Chrysler Crossfire Coupe Limited, 1999 C280
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I'm guessing now; but I have read a similar post (can't remember off-hand) about a part called the OVP relay (Over Voltage Protection Relay).

It MAY be this.

Do a search.

Good luck!
 

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1995 C280 (165K mi)
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It could also be a problem with the crankshaft position sensor. it throws no code but I believe is temp sensitive when it is going bad.
 

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Discussion Starter #6
I was testing it this weekend and found out following: when engine is cold it works pretty much normally. And does so even when it gets warmer as long as it doesnt get parket for a period of time. However if I go and park the car for 1/2 hour or more and engine is still warm it will show simptoms described above. After I drive for a while (quite some time and on the open roads) it will resume working pretty much normally. I am puzzled.
 

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1995 C280 (165K mi)
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yup. investigate the crankshaft position sensor some more. search and read up on it. lots of posts on that on this forum.
 

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Discussion Starter #8
Took it to repair shop and MAF seem to be what caused the problem. And I think they said that they also needed to clean the throttle body.

Thanks all for help!
 

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1995 C280 (165K mi)
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good. that is a simple fix! make sure he actually confirms that it is the MAF. there are tests he can do to confirm that.
 

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C220 1996, C300 2010, E240 2005
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56 Posts
Bad MAF Behaviour

Even when it will not cause the engine to shut down, you will see the idle RPM is not steady.
I also noticed that when it is more humide, behavior tends to be worse.
 
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