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Mercedes Benz C Class 1.8 2003 - Misfires under light load - Fixed #

Posted by Dave Emm on June 29, 2009, 5:37 pm

Year of Manufacture *: 2003
Engine Code or Type *: 27194030191127
( Optional ) Scanner used: star

this one missfires under light load,no fault codes, have changed plugs and coil extensions,also substituted each coil in turn for a new one but no joy. does'nt seem to missfire if you really welly it. was told that the maf can give similar symptoms but reluctant to change it willy nilly as rather expensive. would appreciate any help cheers dave.

Re: merc c class 1.8 missfire under light load

Posted by aidan birley <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT2879' width='330' height='300' border=0 style='border:none;'> on June 29, 2009, 7:21 pm, in reply to "merc c class 1.8 missfire under light load"
Aiden Birley

Hi

Have you checked inlet for air leaks ?

Fuel trims can give clues to MAF condition.

Have you tried with maf disconnected ?

Gas readings may be helpful.

Is the lambda sensor switching OK, if misfiring may up set that.

Fuel pressure and Compressions OK ?

Cheers Aidan

Re: merc c class 1.8 missfire under light load

Posted by Alan Kane <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT5535' width='330' height='300' border=0 style='border:none;'> on June 30, 2009, 11:16 am, in reply to "merc c class 1.8 missfire under light load"
Alan Kane - Administrator

Are you sure its an engine misfire?

That EMS is very quick to log misfire codes and if you can feel them the EMS can detect them.

Assuming its an auto, did you check trans for codes?

Re: merc c class 1.8 missfire under light load

Posted by john white <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1071' width='330' height='300' border=0 style='border:none;'> on June 30, 2009, 9:08 pm, in reply to "Re: merc c class 1.8 missfire under light load"
Tony White

hi dave,

is it an automatic?

john

Re: merc c class 1.8 missfire under light load

Posted by martin stackemann <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1721' width='330' height='300' border=0 style='border:none;'> on July 7, 2009, 12:38 am, in reply to "Re: merc c class 1.8 missfire under light load"
Martin Stackemann

Hi Dave dont know if you've sorted it but I've just done one and it was air leak from breather pipe split you have to remove air filter box and it's under box and goes to crankcase costs about £5 hope this helps Martin

Fixed #

Posted by Dave Emm on July 10, 2009, 4:48 pm, in reply to "Re: merc c class 1.8 missfire under light load"
Message modified by board administrator July 13, 2009, 3:38 pm

hi everyone, turned out not a missfire after all but the auto box juddering, caused by coolant seeping into the transmission oil. new rad, transmission oil and filter change, back to normal. not sure if thats what you were going to say john, but thanks to everyone who replied

Re: merc c class 1.8 missfire under light load fixed

Posted by Alan Kane <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT5535' width='330' height='300' border=0 style='border:none;'> on July 11, 2009, 7:43 am, in reply to "Re: merc c class 1.8 missfire under light load fixed"
Alan Kane - Administrator

Just to add a little to this. The light misfire feeling is caused by the torque converter due to the coolant contamination. The way to diagnose it is to serially switch off the converter lockup. On this model there is an incremental lockup on all gears.

Re: merc c class 1.8 missfire under light load fixed

Posted by john white <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1071' width='330' height='300' border=0 style='border:none;'> on July 12, 2009, 8:59 pm, in reply to "Re: merc c class 1.8 missfire under light load fixed"
Tony White

hi dave.
yep spot on,had one a few weeks ago,had to have box/convertor overhauled,when gearbox drained had loads of coolant in oil,common fault.
glad u sorted it.
john

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