miket0072003

My 2006 C230 Sport with 176,000 miles started running bad like it was running on 4 cylinders yesterday. Hooked up the scanner and got codes p300, p302, and p304. p300 is multiple cylinder misfire, p302 is misfire on cylinder 2 and p304 is misfire on cylinder 4. I replaced the plugs about 10,000 miles ago. I can't remember what kind, but I used what was recommended in the manual. I checked the plugs, they looked good. I cleaned the MAF sensor. I checked the fuel pressure, it was about 54PSI. I sprayed carb cleaner around all of the vacuum lines and listened for change in RPM to check for leaks, didn't notice any change. After all of that, I test drove it and it ran fine until I got back to the house and it started running rough again with the same codes. I checked a few more things then test drove again and it ran fine. My wife drove it today and said it runs fine. With the problem being intermittent, I don't think it would be bad coils, injectors, or wiring. Since the misfire is on opposite sides of the block, I don't think it would be manifold problems. Could this be caused by bad gas?

blzdout

I used to get multiple cylinder misfires until I got a new MAF. Changed spark plugs and everything, still had multiple misfires. Didn't get a code related to the MAF until it went to complete crap, couldn't even get my car to run on the first start. The MAF didn't give my car the correct air & fuel ratio which would cause it to run like crap. A semi failing MAF = no MAF related codes.

But all the possibilities would be:
MAF
Faulty/clogged fuel injectors
Bad Coil packs
Spark wires
Dirty Throttle body
Wouldn't think it would be the fuel pump since your psi is good

miket0072003

blzdout, thanks for the info. I cleaned the MAF sensor with some MAF cleaner spray. The problem went away, but I can't say for sure that's what fixed it. I'm thinking it may also be bad gas or the MAF is going bad. It has ran fine all week.

blzdout

No problem. I'm glad your problem is gone. You never know with these cars, but my money is on the MAF since this is basically a common problem with these cars. And I would think bad gas would cause all cylinders to act funny since every cylinder is getting the same gas.