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  #1  
Old 04-19-2006, 11:49 AM
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Misfire....

Just got my W202 1.8 Elegance back from having a new cylinder head gasket fitted only to discover that it is misfiring badly under heavy load (foot to the floor) from cold start.
I tried flooring the accelerator with gearbox in park, and it revs to 4k and starts misfiring, sounds like rev-limiter cutting in!
Any ideas out there?

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  #2  
Old 04-19-2006, 02:01 PM
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Not the best way to treat a cold engine!! Does it misfire under load when fully warmed up?
The misfire at 4k when in P or N is normal ,as you say it is the rev limiter.
May be the ignition wiring loom shorting out as it is prone to the insulation breaking up ,and has been disturbed when your head was removed to replace the gasket.
Geo.
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Old 04-19-2006, 02:50 PM
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I suspect wiring harness, due to the recent head work. Do a search - there is a post with pictures of what to look for as well as symptoms.
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Old 04-20-2006, 04:28 PM
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Quote:
Originally Posted by shandy
Not the best way to treat a cold engine!! Does it misfire under load when fully warmed up?
The misfire at 4k when in P or N is normal ,as you say it is the rev limiter.
May be the ignition wiring loom shorting out as it is prone to the insulation breaking up ,and has been disturbed when your head was removed to replace the gasket.
Geo.

Why should rev-limiter cut in at 4k when the rev counter red lines at 6k+ ??
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Old 04-20-2006, 04:41 PM
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Quote:
Originally Posted by myheadhurts
Why should rev-limiter cut in at 4k when the rev counter red lines at 6k+ ??
Why would you want to rev an engine in park or neutral, beyond 4 k rpm ?
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Old 04-20-2006, 05:23 PM
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Quote:
Originally Posted by manny
Why would you want to rev an engine in park or neutral, beyond 4 k rpm ?

I don't.....but in a effort to find out WTF is wrong when I accelerate from cold start, I 'blipped' the throttle and found at 4k it mis-fires like mad!!
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  #7  
Old 04-20-2006, 05:34 PM
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Quote:
Originally Posted by myheadhurts
Any ideas out there?
I have an idea. Take it back to whoever did the HG work and have them FIX the problem.
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Old 04-21-2006, 05:55 PM
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Quote:
Originally Posted by 1991300SEL
I have an idea. Take it back to whoever did the HG work and have them FIX the problem.

I have taken it back and it is being fixed ATM. That was not my point.

I would really like to know if it is correct for the vehicle to mis-fire at 4k with no load??
Is it a fault or do MB program this in?
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  #9  
Old 04-21-2006, 06:58 PM
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The rev limiter is set to cut in at @ 4 000 rpm, with NO LOAD on the engine.
It's a safeguard against conn. rods playing peek-a-boo out of the side of the engine block, or pistons playing look-at-me out of the hood,...... I mean " Bonnet ".
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Old 04-21-2006, 07:23 PM
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As I already said, IT IS NORMAL , all modern MB engines are fitted with rev limiters , 4000rpm P or N . There is also a secondary rev limiter which cuts the engine at the red line ; revs dependent on engine type.
Geo.
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  #11  
Old 04-22-2006, 07:33 AM
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I had similar problem with mis-firing turned out to be cracked distributer cap.

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