Whitec250

Hey folks,
I know its a misfire on #4. The engine has a very slight miss ONLY when cold at first start up and last for 30 to 45 seconds, this will happen every morning and eventually throw the code after say a month. After the 30 seconds or so the engine is smooth and normal, no miss and the car runs well all day long.
I've moved coils to other cylinders and the miss code stay on #4. I've changed spark plugs ( NGK 93911 LKR7AIX) on all 4 cylinders.I'm using Shell gas 93 and have run sea foam once .
Now is there a sensor that controls fuel and or spark on cold startup ?
I'm kinda at a loss.
Any ideas ?
2013 C250 45,000 miles

Thanks

meazz1

I had the misfire issue as well but tittle different from yours..
I had a P0302 so I moved the coil to cylinder #1. The misefire did not come back for a while but finally got P0304 in the morning and by the afternoon car shaking so much at idle I was scared driving home work.
I replaced all 4 plugs and coils and car has been smooth as butter since.

Whitec250

So the misfire didn't follow the coil move ?
Well my next step is to start replacing coils. I don't think it can be an injector car doesn't have that many miles and is smooth as butter after 30 or 40 second's.

meazz1

No, it did not follow the coil.
I told myself this " the coil on #2 was probably loose and fixed itself when I moved to #1 but #4 just failed later". One thing thou, the car never was so smooth after the initial problem but never threw a code.

Whitec250

Thanks
Mine just does it upon cold start up sitting for 3 hours or more and then cleans itself up. I may go buy one MB spark plug and see if this fixes it maybe MB doesn't like NGK lol.
Then I'll order a coil and put it on #4.

Where the heck are the fuel injectors located on this thing ?
Very frustrating. Thanks

Jaimemb

Figure it out mate?