Andrew Brenner

Hi All. Love the forum and appreciate any advice. Thanks in advance!

Couple weeks ago did the typical oil change and replaced air filter on 2009 ML350. Saw some bugs and mild debris in the air cleaner, so washed it out and pretty sure was fully dry before installing filters and putting back. At the time, noted rattle on passenger side of engine block. Does not increase with revving, and disappears behind engine noise.

Monday, due to gas station out of gas (in Texas) near our house, wife chanced it and came home instead of going to another. Used gas from the gas can to make sure enough to get to station in the morning, was probably about 4 months old. No problem, but then stopped at gas station Tuesday and all they had was regular unleaded. She got a quarter of a tank, no problem. Later added another quarter with super (dont ask me why she didnt just fill it up). Wednesday morning, she started having check engine light and engine running rough particularly at idle and initial acceleration. At higher speed less noticeable. Pulled codes and it was engine misfire detected cylinder 1, P301. It was due for plugs, so went ahead and replaced them. Still immediately same code, and same rough idle. I have a new coil on order coming Tuesday, nad have a hard time believing it was the gas since it wouldn't keep coming up cylinder 1, would it?

Question: Am i missing something? Is that rattle something more serious with the engine? Did the fuel mess something up? Any insight appreciated!

Maj. Dundee

NEVER wash an air filter. Replace it.

Yes it could be the gas. What might of happened is the gas partially clogged the injector.

Andrew Brenner

Thanks. Don't think you fully read my post. I did not wash the air filter. Not that dumb. I washed the cleaner to remove any debris before putting in new filters.

I didnt think a clogged injector would produce that code.

Maj. Dundee

Understand about the filter.

As to the injector, they have their own codes but the code would only be stored if the open injection time was faulty at idle or higher RPM and cannot tell you if it is clogged.

Are you sure there aren't any other codes like P0300?

Andrew Brenner

Thanks again for the suggestion. Replaced the coil on that one cylinder, and back to normal! $50 and about 15 minutes of work. No more codes! Runs fine. I guess the fuel issues were just a coincidence.

flybd5

For future reference, any fuel with ethanol absorbs moisture over time. Not a good idea to use fuel stored in a can for four months unless you have mixed it with a stabilizer, and even then, don't use it on your MB, save it for your lawn mower.