cl 420 misfire

[jonnyboy]

Hi all

the new cl 420 has a pretty serious misfire - i think it could be two cylinders. It started a day after i bought it and has remained.

This is the first do-er upper I've had which doesn't have a dizzy.

The car had been laid up for years then put into MB to recommission, from where i bought it with 12m MOT

Where do i start without going down the dealer route?

 

[grober]

If its a W140 COUPE get it to a garage with an old fashioned oscilloscope engine analyser. That way you should be able to pin point the cylinders in question and maybe even the problem. I would then remove the plugs and look for clues there.The valve gear and camshafts are a weak spot on these engines so maybe a compression test might then be in order if nothing else is found. The first thing to check is always ignition.

 

[BlackC55]

It can be plugged into a Star too. Start there. I suspect a coil pack.

 

[quasarman]

I had a similar sounding problem on my C320 that grew and grew until it died completely. It started following a major service including a replacement fuel filter, turned out to be a blockage in the fuel rail which once bled completely eliminated the problem.

You might be this lucky too...

 

[jonnyboy]

If its a W140 COUPE get it to a garage with an old fashioned oscilloscope engine analyser. That way you should be able to pin point the cylinders in question and maybe even the problem. I would then remove the plugs and look for clues there.The valve gear and camshafts are a weak spot on these engines so maybe a compression test might then be in order if nothing else is found. The first thing to check is always ignition.

Interesting your note about the valve gear as she has one noisy tappet. Not convinced that is the cause though as the guy i bought it from (an mb service manager) said it had been like that all the time (he recommissioned it following a bereavement long lay-up) yet it had mot'd ok, would have thought it would have shown poor emissions.

 

[BlackC55]

The 119 engine suffers with the oil feed pipe to the tappets falling to bits thus starving the tappet(s) of oil. Quite an expensive job to get done but all do-able. i have one in Tuesday to do.

 

[jonnyboy]

The 119 engine suffers with the oil feed pipe to the tappets falling to bits thus starving the tappet(s) of oil. Quite an expensive job to get done but all do-able. i have one in Tuesday to do.

Could you expand on that a bit Ollie? I definitely only have one ticking on the n/s bank.
Silly question - how do you know which one to do, or do you have to do the lot?
I'm wondering if it could just be a coincidence because of it standing for so long.

Did you sell your Star by the way?

 

[BlackC55]

Stll got the Star.

You replaced the tappet(s) that are nearest to the failed feed pipe.

 

[jonnyboy]

Thanks Ollie