MaxxAction

Hey guys...

I just picked up an 06 C230 Sport.

When I went and looked at it, it was missing pretty badly, so I went back home and got my scanner, and went back and checked the codes.

There were 7 of them stored.

P0021
P0049
P0102
P0300
P0304
P0305
P0306

So, I spent about a half hour on the guy's laptop doing some reading, and came to the somewhat confident conclusion that the MAF was causing most of the issues. The oil looked dirty, so I figured an oil change would take care of the cam sensor solenoid code, and I spotted that the evap connector had had the wires pulled out of it, and that was the evap code. For most of this, it appears I was right.

So I end up buying the car for 2k, because of all the issues. Took it home, swapped the MAF for a new Bosch OEM one, gave it an oil change, changed the oil and filter, cleared the codes, and started it up. For a few seconds it sounded normal, then started missing again, not as bad, but it had a single cylinder miss.

I let it idle til it warmed up, shut it off, and read the codes again. P0305 was all the came up. The coil on that cylinder had been replaced, it looked new in fact, so I ohmed the injector, and it looked close to spec, 16.3ohmed it again, 0.0, ohmed it again, 11.6, one more time, 12.5. So I figured the injector was flaking out, and replaced it, cleared the codes, and started it up. Still a miss, and when I revved it, it got worse. Shut it off, read the codes, P0300, P0304, P0305, P0306, and no other codes.

I did a pressure test to listen for leaks, can't find any significant vacuum leaks. One tiny one on what I assume it the PCV valve. but not enough to cause all three cylinders to misfire. The exhaust on that side has been completely replaced at some point in the recent past. Both cats have been changed, and the front o2 looks new. I didn't get it up in the air, so I couldn't see the rear o2 well enough to see if it looked new.

So I warmed it up and did live data, and a couple things stick out at me. Bank 2 o2 sensor 2 is showing zero voltage, both upstream cats are showing the same temp, short term fuel trim on bank 2 is way high, like plus 30.

I am kinda thinking that there is an issue with a cam sensor or magnets. Anyone have any input on where to look next?

I appreciate any and all help greatly.

MaxxAction

So I think I figured out the problem. Number 5 has almost no compression. I was reading live data tonight, and noticed that I was getting positive pressure in the intake when revving the motor on the MAP sensor reading. I have spark on that whole bank, and all the injectors ohm out good. I think the blow by is bad enough when revved to induce misses on the two cylinders in front and in back of that one. So, can anyone tell me what is the most likely culprit? A stuck or broken compression ring? Carboned up valve? Burnt valve? Thanks in advance.

Russell Ormerod

Do a cyl leakage test. Most likely a leaking inlet valve on that cyl with no compression

MaxxAction

Yes...

I did tonight, and that is the issue. I turned the piston to TDC, and filled the cylinder with a can of seafoam, and pulled the fuel rail and put a half a can of deep creep penetrant in through the injector port. Gonna let it soak for a couple days, then do the whole upper end clean on the motor.

A little story about deep creep that some of you will find interesting. I had a turbo off of my Z32 coke up and seize. A friend of mine recommended that I soak it in deep creep. I bought a gallon of it, and submerged that CHRA in it. For the first 48 hours or so, it didn't seem to do much. On the third day, I could turn the wheel. Every time I would spin it back and forth, it would puke out a bunch of black garbage. By day five, that turbo was perfectly clean and spun like a new one. I put it back on the car, and used it for another ten thousand miles. I parted that motor to do an LS conversion, and sold those turbos three years ago, and the one I treated with that stuff is still working to this day.

Russell Ormerod

Sounds like good stuff, but if the valve does not seal no magic is gonna fix it other than good old elbow grease

MaxxAction

You may be right...

but I hope not. Not feeling like pulling the motor.

Russell Ormerod

Just remove the head, I have done a few

MaxxAction

What do you do about the timing chain?

Russell Ormerod

Remove the tensioner and it can just lay loose in the block, check valve timing before you strip it and replace the chain if neccesary. No need to remove the engine