smint007

w220 s320 gas

so getting error codes p0300, p0301, p0302, p0303. So basically it tells me the cylinders are misfireing and random missfire. So since it goes on several cyllinders I guess it cant be the 3 wires, coils nor spark plugs, what else could it be that missfires 3 cylinders? and when I erase the codes there are none until I do kickdown and overload the engine.

compaddict

iTrader: (1)

I had that same problem and I hate to even mention it because it is so rare.
I had a faulty #4 fuel injector. So rare...

ibeforreal

Try putting some Chevron Techon fuel system cleaner. Pour the entire contents into your gas tank and then fill up the car. Take it on a very brisk drive for about 1/2 hour and see if that has any effect on the misfire.

Jack_88

It never hurts to check the plugs, you can learn a lot from what they look like.

smint007

Can it be caused by a small leakage in the refrigerant?

compaddict

iTrader: (1)

The other thing I saw once or twice in my searches was a bad cat.

DrDoe

I tried Techon cleaner and haven't able to resolve #7 misfire on my car yet. I replaced the fuel filter then filled up 3 tanks with Techon each time. I thought the Techon cleaner might caused gum up so I put in another fuel filter but nothing changed.
My symptoms with #7 misfire: a long delay for the engine to start up after I turned the key. Would the fuel pump or the fuel relay caused #7 misfire issue?

Jack_88

I don't see how the relay would, but a failing fuel pump could cause a misfire.

DrDoe

I thought so too but I mentioned the relay because it's just weird that I don't have the relay in X. In the fuse chart, it mentions relay in X for 12TT AMG and relay in T for other models.
Is there a 12TT AMG separately from 12TT?

Jack_88

S65?

DrDoe

I think you are right. I forgot about that monster.

DrDoe

The bad fuel cap or bad idle air/speed control valve could also caused misfire right? How likely are they on #7 when the engine is cold?