underman

I have 2007 clk350 Cab. 95,000 Mi. Last week I noticed a misfire when accelerating from a stop when the car was first used in the AM. When the car warms up about 10 minutes of driving...everything is back to normal for the rest of the day. At no time did the CEL come on.


I miss diagnosed the problem as a transmission slipping problem...so I called my MB dealer and he suggested he read the Trans codes and do a trans flush. So fast forward to the dealer....No trouble codes in tranny and did the Flush ($389.00).
Now still have the same missing problem in the morning. I am not upset about the flush as I believe it was a good idea under any circumstances.


Today I got the car to document the Mis-fire in the morning by stepping down on the gas harder then I normally do. The car was missing badly and did throw the CEL. I pulled over shut it down...restarted CEL went off and everything (like always) was back to normal for the rest of the day....smooth like glass.


So here are the codes: P0301 and P0 351. (Both for Cylinder 1) Now please note that I have had the P0351 code pop up for the last 3 years....and the car ran perfect. I had told the dealer about it and he said not to worry.


Tomorrow I am replaceing the plugs....do you thing I should try and switch coils with one of the other ones in the bank...and then scan for trouble? Or ant other Ideas would be helpful....Thanks!

Rudeney

First of all, a transmission service is always a good idea - you need it done every 40K miles.

As for working on the misfire, do only one thing at a time. My recommendation, since you seem to be able to reproduce the problem, is to swap coils from cylinder 1 with another cylinder. Then try to reproduce the problem and see if it stays with 1 or moves with the coil. Obviously if it moves with the coil, then you have found the culprit. If it stays with cylinder 1, then replace plugs. If the misfire then continues on cylinder 1, start looking at injectors.

underman

Thanks Rodney!
Here is were I am:


Changed plugs....they were really shot. So now the miss is really pronounced when in drive and idling. So today I swapped the #1 and #2 Coils and the trouble code followed....went from P0351 to P0352.
Question....Can I replace just one new coil or do I have to change all? Do you think this will solve the problem?


Thanks!

Rudeney

Sounds like a bad coil, and yes, you can just replace then one at a time - no need for all.

underman

Thanks Rodney!


Do you know what brand MB uses? I can get Delphi or Bosh. very close to home.

Rudeney

Between Bosch or Delphi, I'd just get the least expensive one.

underman

Installed the new coil and everything is good to go!


Again...Thanks Rodney for your guidance.


Richard

cstevenson

I've had similar bad luck with the EGR valve causing a shaking/rough idle. Each time, the problem has been with the vacuum lines connected to the EGR, they were either old and cracked, or loose.

Rudeney

Glad to hear it's fixed!

underman

Thanks for the input. My problem turned out to be a Coil.


Richard

benzdiyer

By chance, have any of you had a vacuum leak that would only impact a single cylinder (misfire)? I'm experiencing some issues with a misfire on cylinder 2. So far I have replaced the spark plug, swapped fuel injector and coil pack with cylinder 1 but the problem didn't follow. Compression test shows the same for all cylinders (185psi). Manifold air flap lever doesn't seem broken.

Now I'm trying to research and find the easiest vacuum line to perform a smoke test. This forum seemed to be a good place to get some suggestions. If you happen to have a vacuum map for this car, please pass along... that would really help.

Car: 2007 CLK550 (Out of range of balance shaft issue); 177,000 miles

Pending Fault Log
------------------
P0302: Cylinder 2 Misfire Detected
Historic Fault Log
------------------
ECU reports no historic faults
Other discovered fault codes
(possibly pending, current or manufacturer specific)
----------------------------------------------------
P0629: Unknown code
P0645: A/C Clutch Relay Control Circuit

Rudeney

I can't imagine a vacuum leak would cause that. It could be the ECU or the wiring.

benzdiyer

Thanks for the suggestion. I'll be able to continue troubleshooting next week. I'll let you know if I make any progress.

-Freddy

Ghennes13

2005 clk320
122k

took the car in to have the valve cover gaskets replaced. No idle issues ever on this car! Work was completed and drove the car home. Now the car shakes after stopping almost like it wants to cut out and acceleration is choppy. Seriously the car was smooth and never ran rough like this before. It felt perfect the day prior to this repair. No CEL came on. What could have caused this?

Rudeney

My guess is a vacuum leak caused by a broken hose. The rubber and plastics in the vacuum system tend to get brittle.

Ghennes13

Thank you for the response,

I hope that’s what the problem is. Would they be able to find the leak with a scanner?

Rudeney

No, probably not. Tracing down vacuum leaks can be a challenge. Visual inspection is the first step. After that, there are several methods you can use. Some people spray "starter fluid" on the hoses and lines to see if anything sucks it in and changes idle. Some people use cigar smoke and watch for it to be sucked into the hoses.

Ghennes13

It’s funny that my car is running like this after replacing something that has nothing to do with the performance of the engine. We shall find out what the issue is soon enough. Thank you 🙂

Rudeney

The valve covers have breathers on them with vacuum hoses attached to vent the crankcase. They would have been removed when doing the valve cover seals, and those hoses are notorious for being brittle.

Ghennes13

Just got word back from the shop. They said two of the spark plug wires are causing a misfire. Apparently the wires have not been changed. Would it be ok to replace the two that are defective or do they all have to be replaced???

Rudeney

There's no reason to replace wires that aren't bad.

Ghennes13

So the fact that they are 12 years old makes no difference?

Ghennes13

So frustrated!
They replaced all spark plugs and wires but the car still shakes! It happens after coming to a full stop and when you start to accelerate it hesitates until you get to a higher speed. What the heck is going on?!
What if something got in the engine when they replaced the valve cover gaskets? Don’t understand why this is happening now.

Rudeney

I'm still thinking it's vacuum related. Spark issues would likely throw misfire codes. A lean mixture may not.

Ghennes13

Ok so I guess the problem is solved. I drove it home and the car runs and accelerates very smooth. The problem was something that has to do with updating the adaptation on the sts or something. After doing that it runs perfect. I couldn’t really understand but as long as it’s fixed I’m happy!