CLK 200K Misfire

lyrobertson

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Hello
First post so please bear with me!
I have a 55 plate CLK 200K, 44K miles. A few months ago my engine management light came on, was going up hill, about 4000rpm, then loss of power and the car drove like a pig. Was all fine again after i switched the engine off. Happened a couple of other times.

Went to Merc dealer who told me that it was likely to be 'sticky' values and would need total engine stripped down (not cheap!). Fault code was misfire on cylinder 2.

He swapped over cylinder 2 and 3 just to check it wasn't anything else.
Car then ran fine for 3 months, no problems, high revs, uphill, flats, perfect.
Then fault back again yesterday.....

I just can't understand why if it was a mechanical fault it went away for 3 months??

So we have bought a replacement coil pack to try that, but we don't know which cylinder is number 3 (where hopefully a faulty coil pack is now sitting and not an expensive new engine) Is is just as simple as the third one from the front, or is it in reference to the firing order?

Any help or advise would be gratefully received.
Many thanks
Lynnehttp://forums.mercedesclub.org.uk/images/smilies/icon_smile.gif
 

Alex Crow

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yes, it is as simple as the first one from the front.

any chance of those fault codes from the dealer? would likely be p0302 cylinder2 misfiring damages TWC. some of the 271 engines like yours suffered poor valve seating and need either new valves, guides and seats or just valve seat refacing depending who you ask. we have done just one of these to the latter spec (by a professional machine shop), expect to pay around £900 all in. a compression test may prove diagnostic.
 
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lyrobertson

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Hi Alexander

Thank you so much for getting back to me.

I don't have the actual codes, however they did do a compression test which was totally fine, which is why they tried to swap the coil packs over. The car drives great, just totally random if and when the fault happens in total it has happened 4 times in just over 3 months. I drive the car every day. Last time was Monday, but this morning the light had gone off again, all very strange!

Do you think we are wasting out time trying the new coil pack ?

Thank you
Lynne
 

Alex Crow

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who knows really, it`s certainly cheaper than the other option!

i don`t really see ignition coil problems on anything post 1998, not even on the 112/113 engines as others do (usually ht lead problem on these).

here's a question, does it ever idle (tickover) very roughly? this goes with the valve problem scenario. obviously spark plugs should be changed at correct intervals, and your dealer should have put in a new plug with the coil swap really. i would suggest you at least have your fault codes read now the diagnostic swap has been done , are you anywhere near suffolk ;)
 
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lyrobertson

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Hiya

No idle problems - smooth and constant, no noises, rattles, nothing!! Car always been main dealer services - due for one in about 4K.

We will give the coil pack a try and see what happens - sadly Suffolk not handy - I am in Glasgow! I am just hoping that it is something simple as the sticky valve thing just doesn't seem to add up, as the car runs perfectly.

If it was a sticky value problem would it be constant or would it be intermittent like this? The misfire clears the minute I restart the engine, and after a day or so the engine management light goes off.

Thank you for your help.
 

television

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If this was the valve seats or head the fault could not have corrected its self for 3 months,,so coil pack or injector.

the faults on the 271 some years back were where the valve seats cracked and new heads needed,,but I cannot see that being needed here
 

Miffy

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get yourself a ODBII code scanner. read the values for the misfires, move the coil packs to a diff pot, reset the errors and retest, see if the error stays with the pot or the coil pack
 
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lyrobertson

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thank you Malcolm and Mark

We will try replacement coil, injector and spark plugs in cylinder 3 and see what happens.

I did think it was unlikely that a major mechanical fault would go away for 3 months, and after just a simple restart of the engine....!

Fingers crossed

Lynne
 


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