missfiring at tickover 2003 c class 200 petrol

[John Gardener]

I have a big problem that my main M/B agents do not know what the problem is! , C Class 200, Komp, Petrol 36000 miles from new, car runs like a dream, perfect UNTIL I sit at the lights or a traffic jam, the engine starts to missfire as if running out of fuel, or as if someone is taking the plug leads off, one by one, after 20 seconds idling at tickover, so I switch off the ignition, and restart at once, and the cars perfect all day, no misfiring, UNTIL the next set of Red lights, and so the problem starts again! EMU light goes off and on, day by day! its a right pain having to switch off 20 times a day in traffic! its been like this for months, so I gave in and took the car to my local M/B dealers, they put it on the EMU fault finder machine PC, , and found nothing except pages of the same fault going back months! 2 hours later they said" It needs a new cylinder head, valves and springs, as this multi valve enginge gums up the valve seats, cost £2500, plus vat £3000, oh hang on, , wait a sec, the M/B problem book states that M/B now do whats called an engine burn, where the engine is programmed to get red hot, and burn off the gummed valves, cost £100," so i let them do it, it took 1 hour, result, the car has much more power, BUT THE PROBLEM STILL EXISTS! they have tested the plugs, electrics, fuel injection jets etc, they now want it back to do a compression test! I dont think they know what to do! HELP PLEASE!

 

[rpe2]

I recall that the M271 engine does suffer from sticky valves. Before going down this route, be sure it is not a coil pack going south.

Richard

 

[E.D.]

What kind of engine has your car, M271 oder M111?

 

[John Gardener]

Miss fireing engine

Hi Guys, Thanks for any help, its a W 203 engine, 2003 model, 4 cyl Komp petrol injection, I am ex motor trade garage owner 1958 to 1985, I know all cars inside out, even early Mercs, the 1950s to 1960s range, (the good years) BUT NOT modern cars! I cannot understand how switching off the ignition, and then starting up again within seconds, CLEARS the fault! A coil or coils would be intermitent, not breaking down at 20 seconds?

another so called M/B specialist told me, "When the engine is ticking over, the valves have not so much,"bounce back" closing pressure, (RUBBISH) so they then start to stay open a fraction, The engines EMU system knows somethings wrong, and shuts down the amount of fuel to ALL the cylinders to save neat fuel going down ALL the bores! when I switch the Ign off, it resets the EMU again and off we go again, perfect, until the next time the engine has to tickover at the lights, or traffic?? I also know that the valves in this engine are not like the earlier Mercs, nice and big! but tiny ones, like motorcycle valves, and 4 valves per cylinder, strange I am being told they all are gumming up, and why did the "burn off" not cure it! over to you guys! Johnny G

 

[John Gardener]

Well guys, car went back to main agents, for more testing, keep it all day, (no charge) they say compression down on 1 cylinder, so a new head and valves and springs! with labour, and VAT, about £3000! but they say that they will try and reclaim some money back back from M/B, as the car came from Lancasters M/B main agents as a demmo car at 18000, miles BUT I have only done 18000 in 5 years! not very good for a Mercedes is it?? if you have any thoughts on this problem, let me know, its not going in for a few weeks, Regards Johnny G

 

[c240yaz]

Well guys, car went back to main agents, for more testing, keep it all day, (no charge) they say compression down on 1 cylinder, so a new head and valves and springs! with labour, and VAT, about £3000! but they say that they will try and reclaim some money back back from M/B, as the car came from Lancasters M/B main agents as a demmo car at 18000, miles BUT I have only done 18000 in 5 years! not very good for a Mercedes is it?? if you have any thoughts on this problem, let me know, its not going in for a few weeks, Regards Johnny G

That is an over estimated diagnostic in my opinion. Go to an independant reputable mechanic for a scond opinion and ask for a free estimate

 

[John Gardener]

Hi C240?? wish I had your first name, but never mind,
OK I had a reply from an M/B indipendent specialist, who said "I think the main agents are not giving you the full truth, and story, and the so called "burn off" is a factory cure, so it should have worked" go direct to M/B at Milton Keynes, and talk to them" plus I have had long talk with another big indi M/B specialist, who as like all who have looked or heard about this problem, agree "It is gummed up valves., a very common fault with this multi 16 small valve engine" and YES it will need the head off, to at least remove the gum, reface the valve seats, and lap in the valves. Labour cost about £1400, £90 pr hr, plus VAT, OR cheaper labour, to fit a new patten part Cylinder head rebuilt with valves, springs, 4 camshafts etc, for a full total of £1800 +VAT? 1 years guarantee, but if a problem after 12 months, M/B will have nothing further to do with me!

so do I stick with the M/B dealer (awaitng costings) and let them try for a 80% part payment, only if a replacement genuine M/B head is fitted, or go to an indi specialist at, £1400, repair, or £1800, new rebuilt head?? over to you. Regards John G

 

[Autofix]

I have seen this problem a number of times. There are actually two possible issues with the head, carbon causing valves to stick or loose valve guides.
I have also seen other problems mis-diagnosed as this issue. If they actually measured low compression on number one then they are probably right. Misfire codes on number one could be a different story.

 

[John Gardener]

Missfiring at tickover

I have seen this problem a number of times. There are actually two possible issues with the head, carbon causing valves to stick or loose valve guides.
I have also seen other problems mis-diagnosed as this issue. If they actually measured low compression on number one then they are probably right. Misfire codes on number one could be a different story.

Hi, Yep sadly they say that they did a comp test and 1 cylinder, it is low at tickover, how the hell thay can test comp with the engine running is beyond me! in my days, it ment removing all the plugs and inserting a hand held comp gauge?
Johnny G

 

[c240yaz]

All this is a lot at 36K miles. I would go to an independent garage. Not Mercedes.

Tell them nothing about what MB diagnosed and told you. Plead dumb and see what their opinion is.

 

[John Gardener]

Misfiring

All this is a lot at 36K miles. I would go to an independent garage. Not Mercedes.

Tell them nothing about what MB diagnosed and told you. Plead dumb and see what their opinion is.

Hi Thanks, booked into another indi specialist, Tidworths, tomorrow in Rainham Essex , found on the web, who when I gave the symptoms , said "thats an easy on to solve" he talked about valves that were outside the engine, ? but knew nothing about gummed up cylinder valves he has 25 years with M/B cars! so we shall see / more later Johnny

 

[BlackC55]

This is a well known issue and I have repaired 3 in the past.

The dealer is probably right in their diagnosis. You have the typical symptoms and miliage of when this fault occurs.

The problem lies in the valve seats. The early engines did not seal well on the valves and this fault is picked up as low compression by the engine control unit so it shuts the injector off to save any more damage. Turning the engine off and back on again re-sets it.

There is a threshold that can be altered with the Star diagnostic machine so the cylinder is less likely to shut off but is not the ideal cure. A New head etc is the only real remedy.

 

[zerocool]

yep I did a head change a few months back for this same problem,cylinder 1 misfire and it was only slightly down on compression,on removing the head and valves,the uneven valve seat was clear to see,it was causing the problem
if you are near to me,I could do the job for you,a lot less than 3 grand thats for sure

 

[John Gardener]

Misfire

yep I did a head change a few months back for this same problem,cylinder 1 misfire and it was only slightly down on compression,on removing the head and valves,the uneven valve seat was clear to see,it was causing the problem
if you are near to me,I could do the job for you,a lot less than 3 grand thats for sure

Hi thanks, did your car have the same tickover problem? its perfect and ok for about 20 seconds, standing in traffic, and then all cyls cut down to a bad tickover? I have no misfiring until that time lap of 20 seconds!
so I switch off the Ign, and restart, the engine is then perfect, and its fine again until the next set of red lights etc??

 

[zerocool]

yeah it shuts the cylinder down once the ecu detects it
mine was just the same,the garage we did the job for had already changed the injector and spark plugs,and were about to change the ecu

 

[John Gardener]

Richard, an indi M/B guy told me today thats hes 100 % sure its number 1 coil pack thats faulty, would this give the same symptoms at tickover? hes so sure he will not charge me any labour and refit my old coil pack for free! if hes wrong?? any thoughts, John

 

[c240yaz]

Richard, an indi M/B guy told me today thats hes 100 % sure its number 1 coil pack thats faulty, would this give the same symptoms at tickover? hes so sure he will not charge me any labour and refit my old coil pack for free! if hes wrong?? any thoughts, John

Looking forward to hear the final outcome, and how much it cost to repair.

Remember to let us all know.

 

[John Gardener]

Hi Richard, re the coil pack, my latest indi M/B garage today said without doubt, "its the coil pack on number 1 cyl," so confident, he would not charge labour to try a new coil pack, and not charge for the coil pack, that he would not use if he was wrong! and refit my original for free as well! and he in 20 years repairing M/B cars has never heard of valves gumming up on this model, any thoughts Reagrds John

 

[c240yaz]

Hi Richard, re the coil pack, my latest indi M/B garage today said without doubt, "its the coil pack on number 1 cyl," so confident, he would not charge labour to try a new coil pack, and not charge for the coil pack, that he would not use if he was wrong! and refit my original for free as well! and he in 20 years repairing M/B cars has never heard of valves gumming up on this model, any thoughts Reagrds John

At these costs, your on a winner ! When will you have the job done ?

 

[jaymanek]

Hi Richard, re the coil pack, my latest indi M/B garage today said without doubt, "its the coil pack on number 1 cyl," so confident, he would not charge labour to try a new coil pack, and not charge for the coil pack, that he would not use if he was wrong! and refit my original for free as well! and he in 20 years repairing M/B cars has never heard of valves gumming up on this model, any thoughts Reagrds John

cant lose can you..