W220 S500 Misfire

[greatw]

Having a problem with my 1999 S500......

I've got a bad misfire on the left hand cylinder bank and can't (so far) get to the bottom of it.

The cats collapsed after getting a good dousing in water during those little rain showers we had the other week, MB said the MAF was also reporting errors so that was replaced, the cats were then replaced by Dronsfields, but the misfire remains.

The mechanic at Dronsfields sggested it might be the plugs on the way out but it is only due for an A service in 3500 miles and has full history.

Does this sound likely? Could it be the coil?

I'm open to suggestions cos this is getting really annoying

 

[BlackC55]

Plugs

Coils

Leads

Those are the first to check

 

[greatw]

Thanks BlackC55.
It was running fine until I parked it up to go on my jollies (own fault then I guess) so it is possible that the damp has got in and corroded something that was borderline! How many coils feed each bank please and are they on that side of the engine bay? Sorry for what may seem a daft question but i havent had teh engine cover off yet so don't know the layout.

 

[greatw]

The plot thickens...
It appears now that it has no compression in cylinder no 2! This is going to be expensive. The machanic says that tone of the valves isn't closing properly and that (understandably) is the cause.

They are taking the head off in the next day or so to see the extent of the damage but I'm curious what could have caused it!

I have spoken to the dealer I got the car from (non MB) and his take is tough we only give a 31 day warrenty as we are a trade car centre. Needless to say, I have taken this up with trading standards!

I'll give another update once we know what the full extent of the damage is but I cannot see a broken cat causing this damage!

 

[Benzowner]

Sounds like you may have burnt a valve out. This is usually caused by bad timing, spark firing before valve is fully shut, not a normal thing on electronis ignition, unless the damp got in somewhere and messed the timing up.

 

[Dieselman]

When the Cats break up they can spit back into the cylinders scoring the bores as the exhaust pressure builds up behind the broken honeycomb.

 

[BlackC55]

When the cats can break up and sends the ceramic dust/bits up into the cylinder bores prementurely wearing out the cylinder.

This has hapened before but quite rare.

 

[greatw]

Just spoken to the garage.
Looks like it is a burnt out valve :-0
This is going to cost a few quid to fix.
Thanks for the comments guys. I hope that te valve damage is as far as it goes. They haven't finished stripping it down yet!

Never had this sort of problem with my various lexus'ssss (he said diving for cover!)

 

[greatw]

Well, they've had the head off and the valves are OK :bannana:

But

They now think it is a problem with the hydraulic lifters on that cylinder

The mechanic has not worked on one of these engines before and seemed to be under the impression that it is a Hemi type engine i.e cylinders come in and out of service as required. This is worrying.....

Frustratingly, MB suggested that they may be prepared to chip in for the repairs but only if I took it to a stealer for them to investigate. If the fault was not due to a manufacturing or design fault, I would have to pick up the tab, otherwise they would look at making a contribution. This is getting really frustrating now!

Next installment in a couple of days......

 

[Dieselman]

They now think it is a problem with the hydraulic lifters on that cylinder :

Sounds like it probably is. One has jacked up, no big deal, just replace it.
(

The mechanic has not worked on one of these engines before and seemed to be under the impression that it is a Hemi type engine i.e cylinders come in and out of service as required. This is worrying.....

It does, though not by using the valves, just fuelling.

 

[miro]

Sounds like you may have burnt a valve out. This is usually caused by bad timing, spark firing before valve is fully shut, not a normal thing on electronis ignition, unless the damp got in somewhere and messed the timing up.

Damp does amazing amounts of damage.

 

[greatw]

Dieselman, I did not know that!
So if that is the problem, the fix is easy?

Hopefully then, I should have my car back soon. Been driving round in a Vauxhall Corsa borrowed from teh in-laws. Not ba but I hate having my knees up either side of the steering wheel 'cos theres nowhere else for them to go!

 

[Bigmick]

Hi guys, I have a CLK 200, and It going to get me killed. In the last week when i start it in the morning it runs badly with no power until it heats up to 80degree and will misfire out an inlet valve every 20 or 30 seconds. Once hot it will drive but you have to nurse the accellorator to get going, if you push the pedal anyway hard it just dies (whick i found out yesterday as i tried to pass out an old biddy in a corsa, i put the boot down and pulled paralel and eventually had to pull back behind her again coz it would not accelerate. Help please, my Dad (Mechanic) says it sounds like a bent value but after reading some of the posts on this web page i'm fearing even worse.

Bigmick

 

[Dieselman]

Sounds more like the MAF or a coil pack.

 

[BlackC55]

Air mass.

 

[Bigmick]

Guys ye are a life saver, I will check and let ye know.

 

[Bigmick]

Clk 200

Hi guys

I went out to get the reference numbers from the MAF and i pluged it out of the air filter box so i could get a good look at the numbers. I started the car and the ran with it's usual misfire until i put my hand near the air intake and the engine suddenly ticked over perfect, i take my hand away and it misfires again. I have my buddy checking to see if i can buy a spurious MAF from my local motor factors, the aim being if it doesn't work i can return it.

 

[Dieselman]

Sounds like an air leak making the mixture go lean so spitting back.

 

[Bigmick]

Guys it was the MAF and now i.ve got more power now than i had before the MAF went.

Sweet MAF cost me €130. and that included getting it couiered to me, so very happy MB driver here

 

[greatw]

OK to tie this thread up.....
It was a failed valve lifter. All fixed and all working again and the price for the work was VERY reasonable. Took a while and still a bit lumpy on tickover when cold but I can live with that for now!