Misfires & Check Engine Light
My C63 is having CEL and misfires.
At first the codes were P0300 301 303 304
I had all my spark plugs changed and reset the computer. The problem went away and the car drove fine for maybe 30 miles.
Now it has really rough idles and shakes really bad slowing down to a complete stop and accelerating from a stop. It threw similar codes just different ending numbers.
Anyone know what this problem is?
I have headers and midpipes and a tune.




O2 because once the check engine light came on throttle response would go flat...I tune standalone on the side so I understood that ment the ECU was dumping fuel into the engine to prevent a lean condition. dumping fuel ment running rich ment misfire. hard to explain...a lean condition would result in a different throttle response, not flat.
we'll need to know all the details.
Last edited by hachiroku; Dec 8, 2016 at 02:28 PM.
The car just shakes violently when idling, slowing down & accelerating from a stop.
The cars start up is weak and quiet as well, not loud like before.
Going up a hill driveway is hard for the hard, i feel like it has no power and it shakes a bit harder on a hill.
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1st time they changed the sparks and then reset the computer and it was good for a couple hours but then about 30-50 miles later I was driving on the road and I felt that something was wrong with the car(slowly losing power, started to shake a bit) then I came to a red light and it started shaking violently and then the CEL came up flashing and then went solid.
So i went back a second time and the MB technician hooked it up and reset the computers and said something about balance the lean and rich. Then the car was good and so far is still good (I got it back like 5 hours ago)
It's not the same as before though, I still feel like the power isn't all there.. cars has small shakes every now and then.. car startup is weak and quieter than normal... when i drive up my drive way (hill) it shakes a little harder and has trouble getting up compared to before.
I just don't know what the problem is. I read other posts about the P0300-P03### and everyone seems to have different answers... some are leaks, bad gas, sparks, coils, O2 sensors, head gasket, etc..
I can't really just change everything until it goes away because some even say they changed it all and didn't go away.
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1st time they changed the sparks and then reset the computer and it was good for a couple hours but then about 30-50 miles later I was driving on the road and I felt that something was wrong with the car(slowly losing power, started to shake a bit) then I came to a red light and it started shaking violently and then the CEL came up flashing and then went solid.
So i went back a second time and the MB technician hooked it up and reset the computers and said something about balance the lean and rich. Then the car was good and so far is still good (I got it back like 5 hours ago)
It's not the same as before though, I still feel like the power isn't all there.. cars has small shakes every now and then.. car startup is weak and quieter than normal... when i drive up my drive way (hill) it shakes a little harder and has trouble getting up compared to before.
I just don't know what the problem is. I read other posts about the P0300-P03### and everyone seems to have different answers... some are leaks, bad gas, sparks, coils, O2 sensors, head gasket, etc..
I can't really just change everything until it goes away because some even say they changed it all and didn't go away.
Review gas, then check coils, connections...fuel filter, fuel pump....


My C63 is having CEL and misfires.
At first the codes were P0300 301 303 304
I had all my spark plugs changed and reset the computer. The problem went away and the car drove fine for maybe 30 miles.
Now it has really rough idles and shakes really bad slowing down to a complete stop and accelerating from a stop. It threw similar codes just different ending numbers.
Anyone know what this problem is?
I have headers and midpipes and a tune.
http://www.autocodes.com/p0300_mercedes-benz.html




I went to the dealership and they told me this is a normal common issue because my car is modded with exhaust work and he added that my car sounds great. As soon as i heard that I was like this guy is full of **** and is probably planning on making **** up and charging me for **** I don't need.
I am PRAYING TO EVERY GOD out there that its NOT the head bolt issue. I don't know much of the head bolt issue, but heard that it's either going to cause me to dump the car or spend 15-30k in repairs. I tried reading about the issue but don't quite understand it because I don't know car terminology that well.




Where are you located upstate NY? How far is your drive to Long Island?
I have a mechanic around here that worked on my C63 and some other c63's that might be able to help you out. They have a mercedes specialist that works with them so he can probably help you out.
I don't want them saying its the headbolt, making me replace it and then the problem is still there LOL because i might as well kill myself after that.
Also if i replace the headbolt, will the headbolt issue ever come back?
i live like 4 hours away from long island. I would drive there if my car was in good condition but I'm scared to drive it that far since its already shaking and scaring the crap out of me driving from my house down the road.
How many miles on the car?
It would be weird to have both sides fail at the same time, but also could indicate you're having an issue because of the headers as well.
How long have you had the headers on?
And lastly, have you contacted the tuner for possible solutions?
If the problem persists, I would revert back to stock instead of driving it continuously knowing that there is an issue. I know that it is a pain but I'd rather do that than risk damaging anything. Granted, the reason the car is cutting power and such is to protect itself, but if you romp on it the car can only protect itself so much.
Last edited by C SEXY 3; Dec 15, 2016 at 07:04 PM. Reason: stuff
Today while driving it with my mechanic a CEL came on and a new code P2629 (o2 sensor pumping current trim circuit/open bank 2 sensor1)
I have almost 60k miles
Headers i've had for two years already.
I haven't contacted OE tuning yet. I probably should.
The shops want to charge me 1500-1900$ to put my stock system back.




