Wanted to get some thoughts on troubleshooting these two CEL codes that came up last night. Details on the car:

2000 E320
133K Miles


P0204 - Injector Circuit Malfunction in Cylinder 4. Status (Not defined)

P0304 - Misfire in Cylinder 4 Status (Stored)

Looks like Cylinder 4 is having a bad day. The engine is sporadically shaky under acceleration. Odd thing is, the CEL went off on it's own and the acceleration smoothed out...only to return again this morning.

Are there any sensors I can try cleaning? Bad coil? Couldn't find much via searching but hopefully someone can chime in. Thanks!

I had an a Mercedes Indy look at the car and he checked the fuel injector in particular on cylinder four he mentioned it had a good "burn" on it and their wasn't anything wrong with it. He didn't find any electrical issues on the car.

Swap the coil to a different position and see if misfire follows

Update:. Ended up being a bad fuel injector.

I have one coil, that gets green corrosion like battery. I just clean off

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