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Rough Idle: Misfires

955 views 2 replies 3 participants last post by  Patch's 
#1 ·
My car is running fine which makes me very happy indeed.

I realize that this is not for forum for this car, but I am trying to help a friend who is having difficulties with a 2002 CLK320 with the same engine as mine. There are no Mercedes mechanics on the island where we live (Key West).

Car is running extremely rough and stalling out. Codes are P300 (?) and P304 (multiple or random misfires)

Plugs are new. Bosch MAF is one year old. CPS was replaced 2 years ago.

Mechanic said that he was getting bad readings for MAF. He removed the Bosch MAF and put in a new aftermarket MAF. The engine ran great and smoothly for a few minutes and then went right back to running roughly and stalling out as it did before. When the mechanic pulled the new MAF he had just put it, he said it smelled burned.

He checked for vacuum leaks and said that there were none.

His final analysis: He has no clue how to fix the car and suggested taking it elsewhere (he did not charge for his time). He said maybe the problem was electrical, or the computer.

Anyone have an idea of where to look before seeking help off the island?

Thanks
 
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#2 ·
You guys need a real mechanic out there. Anyone who would put in some cheap aftermarket MAF as a test is himself not firing on all cylinders. :rolleyes:

You may want to read through this thread: http://www.benzworld.org/forums/w202-c-class/1587186-p0306-cylinder-six-misfire.html since it's close enough as a place to start.

There's also the vacuum line at the bottom of the front of the manifold that you can't even get to without removing the air injection pump, so I wonder how he checked that one?

Order a scanner that will do real-time data or take it someplace that has SDS or at least carsoft, but you can still try some of the stuff in that 202 thread first, most of it is just plain old diagnostic stuff.

Good luck to your friend.
 
#3 ·
As we can't see or hear what you see on the engine and with no freeze frame data I would pull the plugs on that cylinder and the one next to it don't clean or alter them post a picture when you remove them look at #4 right away don't touch the tip of the plug, is it wet, very damp or bone dry note it in your reply. Ask the mechanic where he got the maf then check for labeling.
patch
 
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