cjimmy

Recently purchased this 08 E350. Changed the oil and it started missing and throwing code P0302. It had the wrong spark plugs in it, changed the plugs and tested the compression. Still throwing the cylinder 2 missfire code.

1 - 115psi
2 - 110psi
3 - 115psi
4 - 120psi
5 - 120psi
6 - 120psi

Those seem on the low side to me, but nice and consistent. Is 110 enough to fire in this car? I have had other cars with less that ran, but am not that familiar with this motor. Swapping coil packs with another cylinder did not move the problem. How do I test the injectors?

Thanks

machild

The minimum allowable reading is 145psi. The cylinder difference limit is 22psi. The testing should be done with the engine at operating temp and the injectors not firing during the testing. Good luck.

cjimmy

Yeah, My test was with the engine cold, and I did not add oil to see if the numbers rose indicating worn rings vs. valve components. All of the coil packs were removed, so nothing was firing. At least I got that part right LOL. To be honest I was looking for really bad numbers below 80 and although not overjoyed with the 110 to 120 numbers those numbers did not appear to me to be the cause of my sudden misfire problem. I'm going to swap some injectors around to see if that causes the problem to move and verify that I am getting power to the #2 coil pack. If I don't learn anything then perhaps I will perform a more thorough compression test with the engine warm.

I don't really want to get the engine up to operating temps while it is missing. Seems to me it would be better to find and fix the problem and get her running on all cylinders before running her up to operating temps. I suppose it does not matter, it just pains me to run a motor that is missing.

machild

Here is the MB procedure for injector replacement.

cjimmy

Thanks!!