w204nyc

I finally got a OBDII reader and yesterday I had a flashing CEL and i was able to oull the code. It said random misfire and the code was P0300. I had the spark plugs and coils, as well as fuel pressure sensor. The car started acting funny and was shaking pretty bad. Only mods are OE tune and no sec cats or resonator. I know a lot of ppl have been saying it could be bad gas and I was using a different gas station and everything was fine. Last night I put gas at another station and 30 min later the CEL came on.

abcut973

Did you empty your tank before filling up with new gas?
As well which cylinder is misfiring? P0300 is the generic code.
You are saying you changed your plugs/ coils and fuel pressure sensor. Could be faulty head gasket .

w204nyc

Yea not sure, it didnt say which cylinder, last time it was 7 out of the 8 cylinders. I didn't empty it but it was pretty close to empty. I've been meaning to clean out the whole tank but have never done it before

rentzington

would a generic code reader pull the detailed info or just the overall error code?
Curious whats required for the detailed info? Star diagnostics?

w204nyc

I'm curious too. I'm using a Innova 3100, reviews were great and its very easy to use. But all it said was misfire, it does show the MAF and sensors data too but the light turned off so I'm not sure what the data shows

SROC276

I ran through similar issues....changed gas to chevron and so far no issues. Also running oetune stage 2. It misfired even after changing fuel pumps, fuel check valve etc. started using chevron only and no issues thus far. Higher ethanol content seemed to cause the issue. 76 gas in my area had the highest according to some mechanics.

SROC276

Seemed to be winter blend formula. A lot of gas in California had to be imported from overseas this past winter due to refining issues in our state. Not sure where you are are. Have heard fro dealer tech this past season saw an increase in number of misfire complaints.

w204nyc

Yea I dont think ive seen Chevron in NYC. I was always putting mobil 93 and i switched to BP and it was working better. The other day i was low on gas and the closest was a Sunoco and thats what I put. An hr later when I started the car, ot started shaking and the CEL popped up.

SROC276

I would finish up the tank and reuse BP...by 2nd tank of BP could be better. Mine would happen usually within an hour of restarting the car when it warm not during morning cold starts. Normally parked the car for under and hour somewhere and then restart it. I would get major shakes and cel flashes. It would disappear if I stop them restart the car.

w204nyc

Yeah I drove the car today for 30 min and then parked For 1hr and left it running. I turned the car off. When I restarted it 30 min later, it started shaking and stalling and wouldn't let me pass 3000k. No CEL came on and i got home just fine. Car felt sluggish the entire way home but no CEL.

SROC276

Yup...every time it shakes...or it's about too...shut down and restart it. Should run fine until you use the BP gas again. Looks like we have the same gremlin. It may be sluggish due to excess fuel in system and exhaust. I could smell mine after a misfire. Would not run it while it is misfiring....just shut down and restart. Try a different gas and see what happens.

w204nyc

Yeah I smelled it too. Sucks not to be able to pinpoint the exact problem. I ran mobil gas for 3 yrs no problems, why now

rentzington

i always buy top tier gas, it may be a marketing scheme made by fuel companies but so far i've had 0 issues on any of my vehicles.

http://www.toptiergas.com/retailers.html

I usually end up at QuickTrip since theyre typically cheaper, or chevron.

if you're using Mobil it should be fine .surprised they still have Mobil stations there, they all converted to Exxon here

Weird though BP is on that list of top tier.

SROC276

Yup same here....misfire issues recently started and I've owned the car about 4yrs too...could be a combination of things and so far no real solutions until mb has an update to handle the issue. For me it doesn't affect anything other than start up which is the common factor. The v12 and new turbo have suffered the most apperently with the winter blend according to my techs reports in the service area. Again I had everything changed and so far only real fix was to switch to chevron or something other than 76 here in California. She'll seemed to cause it once or twice but not as bad as 76 for me.

w204nyc

Yea I'm worried that the mechanic that changed my
Coils and spark plugs might have not
Done it right. They rechanged all the spark plugs and everything was fine and after a week, same shaking problem

w204nyc

Now I got a code P2629. I think thats left o2 sensor. Anyone know the code?

SROC276

P2629 - G3/3 (Left O2 sensor, before TWC [KAT]) : Open circuit , never got the code before...may got fouled or damaged from prior misfires. Would check the sensor and see if can be cleaned or may need to be replaced.

w204nyc

Thanks! I figured it was the pre cat sensor. I guess I'll get that changed

synacide

Same thing happend to mine. check engine light and rough engine. I took it to the dealer, the result was all codes for leak in the evap system. The description on my service sheet says "...closed the charcoal canister valve and pulled a vacuum of 25hpa on the tank and tested for any leaks. did not drop below 5hpa drop for 5 minutes no leak in the evap system. checked the date and part number on the purge valve. saw number falls under conference material in 09 of june. replaced the purge valve. had to install the clamps on the purge valve lines do to they were missing. erase fault codes after."

and then it was fine after that.

w204nyc

Yea my dealership wont go through all of that. They keep telling me
To change my whole exhaust so they wont help me much.
Since its modified they wont warranty anything even with my
Extended warranty

w204nyc

I just got another CEL. Code was P2629. I checked the stats and here is what its showing

Fuel pres. 74.4
MAF 3.0

Still dont know what to do

95gsrturbo

Add an octane booster from local auto parts store.

w204nyc

Thanks, will give that a try!

CarHopper

P2629 is related to the o2 sensors I believe. And a bad o2 will cause the car to run like crap.

Miles on current o2 sensors?

w204nyc

Its a short circuit but I was told not to change it. I replaced it the first time and it went bad after a month