Gummout

[mmarch]

Here's my problem:
I have a '03 w211, E500, engine light came on and it was running rough.
I put gummout fuel injection cleaner in and eventually it ran smoother and eventually the light went out.
after the gummout/fuel was out and I refueled, it started running rough again and it started the same thing again-so I put gummout back in, and it eventually smoothed out.
When that was out of the tank, it started running rough again.
Am I missing something?

[mpolli]

Is the CEL on? Did you pull any codes?

[mmarch]

Yes it is on. It goes out when I put gummout in and the code from it says misfire in cylinder 8. I changed the plugs, coil, and wires before I put the gummout in.

[mpolli]

I am guessing it has 4 coils, is that correct?

[mmarch]

Sorry it took so long for me to respond, but no it actually has 8 coils, 16 spark plugs.

[mpolli]

I wonder if it is possible the code is wrong in some respect. Either calling out the wrong cylinder, or reporting a symptom of another problem. You could try swapping the coils around and see if the code changes. Have you searched? You might find others who have gotten this code and what the trouble turned out to be.

[bobs]

This may be a dumb question but I have to ask it. Do you refuel at the same place every time? Maybe the station you go to has a bad load of gas and you should try and refuel somewhere else.

[mmarch]

No, it's not a dumb question. I refuel at multiple sites. I went to another autozone after the response pertaining to possible wrong codes and this location gave me 5 diferent misfiring cylinders! 6,3,5,7,and 8. Aftr this, I agree it must be the ingnition wires...

[pj67coll]

Wiring harness? Or had that been fixed by the time this model year came along?

- Peter.

[TheDon]

Check your plugs, the injector cleaner could have fouled them. 16 plugs is going to be fun to check.

(also, mercedes specifies to not use any form of fuel additive for any reason other than weather conditions)

[mpolli]

Originally Posted by mmarch

I agree it must be the ingnition wires...

In post 3 you said you changed the wires.

[mmarch]

Yes I did change the wires, on cylinder 8 only, and they came from another Merc; they weren't new. I was just trying to see if there was going to be a change in the misfire...

[mpolli]

Ohm out all the wires

[mmarch]

Already checked the wires, they checked out ok. Checked a few vacuum hoses and they look pretty bad! A lot of cracks and stuff goin on with 'em. I'm also gonna change the plugs. hoopefully that'll do it...