[boilerwings]

Hello,

this is my first post on the forum. I have read a lot of great info here for a few years. I did some searching on other threads but didn't find anything specific to my recent problem.

Driving home last night, was at a red light, all was good. light turned green, the take off was very rough, CEL started flashing, engine running rough, stopped in a parking lot, idle was rough, but CEL went steady. It felt like it was misfiring. Shut the car off, waited about 3 mintues, started back up, no CEL, smooth, normal operation as if nothing happened.

Any ideas? I'm thinking something sensor/computer related since everything returned to normal after restarting the car.

2006 C230, 6-speed manual. It's at the dealership now, but have not recieved a call from them yet.

 

[schumicat]

get an OBD 2 code scanner so you can read the codes yourself, $40 at any auto parts store. the car stores codes (until they are cleared) so even when car is back to normal you can see why light was on. could well be a miss.

 

[i5mast]

Flashing CEL means misfiring.

It's important to know whether the misfiring was contained to let's say one cylinder or random cylinders. I would just wait for the dealership to call you and give a report instead of guessing. There will be some diagnostic codes stored in a computer.

 

[Check Codes]

As i5mast noted, it's a seirous misfire. The car started running rough because the ECU shut down one or more affected cylinders. Restarting reset those cylinders. That's exactly how it is designed.

Since you've left it to the dealer, good luck. Hopefully they don't gouge you too badly.

 

[boilerwings]

Dealer told me the fault codes were:

"Fault code #1- 0629; which is set when there is an engine misfire
Fault code #2- 0653; which singles out the cylinder/s that have the misfire(which in this case was the number 5 cylinder)"

I can't find these fault codes online anywhere.

compressions were good, and he recommended changing the spark plugs. I don't really agree with that as an acceptable solution to the scenario I had. Seems more like a computer or sensor issue to me.

What do y'all think?

 

[a02stang]

how much fuel was in it when it started doing it? is it a ethanol vehicle?

 

[boilerwings]

it has 3/4 tank.

Did some more research and found that those codes are for fuel pump relay shorting to ground. Dealer told me that it was the code for misfire in #5 which is wrong. If it is the fuel pump relay, then that would certainly make sense why it ran smooth again, CEL cleared, after turning the car off and back on.

What irks me off about the whole thing is they wanted me to pay $700 to replace plugs and leads when that is not even remotely close to fixing a fuel pump relay.

 

[rudeney]

These are DTCs specific to MBZ - not generic OBDII "P" codes and they do indicate a misfire, specifically on cylinder #3. Your engine is due for spark plug replacement every 5 years or 91K miles, whichever comes first. If you haven't one that, then I'd look into it. Also, you might swap coil packs to see if the error tracks to the coil or the cylinder.

 

[Eva89]

I recently had the SAME EXACT issue with my 07 C280 a month or two ago. When the bad misfire would happen, usually when the car was under strain, like uphill acceleration, the misfire would eventually become constant and the CEL would flash. Reading the codes revealed a misfire on Cylinder #4 only. I changed the coil ($56 at Autopart International) on cylinder #4 and the problem completely went away and the car ran perfect since. The coil literally only took 10 minutes to fix. If you can put the spare tire on your car, you can change the coil.

As far as $700 to replace spark plugs, that is just complete insanity. The car needs 6 spark plugs, which cost about $12 each, and about $12 for each lead / boot, or $144 for the entire set of plugs and leads. The spark plugs are so easy to change in that car, it would never take longer than an hour to replace all 6. I know because I've done it. Any garage or dealer that would charge more than $250 to change the set of spark plugs is simply raping the customer.

Like Rudeney said, If you have over 90k miles, I would start by changing the plugs, since they are due for service anyway. If the problem persists, try changing the cylinder #3 coil for another $60 and 10 minutes work. If you have good compression, then it is probably a plug or coil.

Also, my car would run smooth again after shutting the car off and restarting. This is because when the computer senses a misfire on a cylinder, it cuts signal to the coil and shuts down that cylinder completely and initiates the flashing CEL. Restarting the car resets this, and it runs smooth again and the light goes out....until it acts up again.

Code 0629 is in fact for "random misfire".
Code 0653 is a misfire in cylinder #3.
These numbers are Mercedes codes, not OBDII codes (which would start with a "P").

Honestly though, if you can change a flat tire, you can change plugs and coils in an hour. It is super easy.

 

[Eva89]

...and this diagram will show you which cylinder is which.