DropGems

Just did ecu/tcu last week. Coil packs failed instantly, car went limp. Replaced right bank coils and sparks. Now getting misfires on cyls 3 and 6 (the one time I had the code read). Check engine always came on when I floored like a few days after I changed the coils and sparks. What could be the culprit here? Hopefully between my mechanic and the tuner, they can figure this out. Thx.

RaceHorse

Assuming everything was installed correctly on the new coils, I'd say Ignition control module. I had a similar situation a few years ago. One coil then the other, followed by another misfire. Ignition control module replaced and everything has been good since.

Dr Matt

Sorry to hijack but I wonder if the ICM is my problem too then.

I loaded my new tune and have tried twice to make a pull but both times I got multiple misfires on the left side of the motor and went into limp mode. Turn off the car, restart & it runs fine. I did clear the codes before trying the second pull FWIW.

That side of my motor has a new style coil replaced at the stealership by the previous owner less than 3,000 miles ago so I did not expect it to fail instantly with a tune. Apparently when the coil was replaced they recommended the ICM be replaced too but the P.O. of my car only had them do the coil & it ran fine until I loaded the tune.

Is there any way to determine if it is the ICM and not the coil?

DropGems

Yea, before it happened like once a day when I gunned it, I would have to turn the car off and restart. It started happening more and more frequently and now it's every time I gun it. Something is screwy.

Dr Matt

Well good news on my misfire problem at least. I called Eurocharged about it since it started immidiately upon loading their tune and they suggested clearing the codes then disconnecting the battery for 3.5 hours to reset the computer. I did this and drove the car a little taking it easy for a couple days because it was raining. Got some nice weather today and opend it up several times with no stumble or misfires. One pull was to about 100 and another to about 120, others just up to 80's.

Seems clearing the computer did the trick, at least for now. Anyone else find they had to disconnect the battery when changing between tunes? In my experience a reflash usually clears any previous adaptations, but maybe not with a Mercedes?

radride

Good to hear.

R.K.

DropGems

Dropping the car off to my mechanic this week. Anything else it could be besides icm? I really want to get this resolved and I want my mechanic to know where to look...

shardul

iTrader: (1)

if coils have been replaced then the next thing to replace is the ICM

DropGems

Okay so it's consistently a cylinder 3 misfire and the Bosch spark plug electrodes were melted off. My mechanic replaced them with NGK spark plugs which are supposed to be more resistent. Said car was running rich and might need fuel filter and other things replaced if it happens again. Picking the car up today.

shardul

iTrader: (1)

pick it up do a couple of WOT runs and report back.
BTW if the fuel filter was clogged the car would start to run lean not rich, hence the melted electrodes

Dr Matt

Misfires cause unburnt fuel to reach the O2 sensors making the computer think the engine is running lean therefore causing the computer to add fuel and giving you a subsequent rich condition. Be sure to clear the computer fuel adaptations by disconnecting the battery for a while after the new plugs go in.

Never a bad idea to replace a fuel filter when having possible fueling issues IMO. I found when doing mine the pressure regulator on our CL65's is actually in the filter so a filter change can alter the pressure and fueling to our motors. For that reason a fuel filter change should also include a adaptation clearing.

A common cause of a single cylinder misfire and melted plug is a bad/weak/clogged injector. If it happens to that same cylinder your mechanic can swap the #3 injector with adifferent cylinder and see if the misfire follows the injector.

DropGems

^ yea they mentioned injectors if it happens again... Will keep you guys posted.