Misfire at high rpm no load - Mercedes Benz SLK Forum

SLK R170 General Discussion SLK 200, SLK 230K, SLK 320, SLK32 AMG

 
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#1 Old 04-22-2012
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Misfire at high rpm no load

Hi all,

Yesterday I noticed a stutter/misfire in my '98 230 (MT) at high rpms (~>3,500) but only seems to occur when revving with clutch depressed. It accelerates fine through the gears both under light and high load.

I have a slightly instable idle and occasionaly the s/c clutch engages at idle even if the engine is warm and stays on for no more than 2-5 secs then disengages with a following short drop in idle rpm. No other engine misbehaviour noticed.

I will proceed to check the K40, MAF and spark plugs now - anyone has any other ideas?

Will appreciate your input, thanks in advance.

Raindog
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#2 Old 04-22-2012
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Update:
Just soldered the K40. It was not nearly as bad as the pics in Bazzles sticky on the topic, but quite a few of the solderings were cracked and needed resoldering.

However, it did not solve the misfiring which still remains. I noticed though that it is only there when the car is at a standstill. When at speed, I can depress the clutch and rev the engine beyond the 4,000 rpm where the misfiring otherwise occurs

Anyone dares a guess at what could possibly cause the described symptoms?

Raindog
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#3 Old 04-22-2012
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Red face rpm limitation

Ok. Did a more thorough search in past posts and found that the engine has a rev limitation around 4,000 rpm when at standstill. Sorry for not finding this prior to my two previous posts.

I must say though that the actual limitation is far from smooth and certainly does not feel intended - It had me fooled thinking that something was wrong.

I guess this is another reminder that these supercharged engines are not intended for high revs. I love it for the low rev torque though and I am happy that what I thought was a problem turned out not to be.

Hats off to these forums and past posts

Raindog
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#4 Old 04-22-2012
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I think you found the "right" answer to your problem - sounds exactly like the rev limiter kicking in...



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#5 Old 05-24-2012
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Thanks for the update! Just replaced the CPS and was having the above issue... thanks for the answer!!
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