VoytekC240

2002 C240 170k miles, has rough idle, misfire and stalls when touching the accelerator.

The car stalled on the freeway and was towed. The codes were P0400, P0301, P0303, P0300 and P0104 pending. I cleaned the EGR pipe, cleaned MAF sensor, cleaned the throttle and checked the tubing for vacuum leaks. I disconnected MAF sensor, no change and perhaps because of it I got P0112 and P0102 codes. I measured the voltage on connector and it was OK. Now everything is connected back, I erased the codes, car starts nicely, runs well on idle initially, then as it gets warm starts surging and misfiring. It stalls immediately when touching accelerator. It run 2 to 3 minutes, no codes. What should I do next? I own the car since new and replaced spark plugs and fuel filter somewhere around 100 - 120k. Has been a while.

johnhef

I'll have to brush up on my P codes but looks like something with the right bank? Cat clogged maybe?

VoytekC240

I checked the fuel pressure and it only shows 5 psi. The engine is not even starting. Trying to, but cannot catch on. I replaced fuel filter and no change. I looked at the fuel pump and it is energizing. I can feel the motor running. I called dealer and they quoted $545 for one fuel pump and said I need to replace second one for $350+ as well. This car has only one fuel pump under the back seat. What is going on? What do I need to replace? Could it be anything else then fuel pump?

johnhef

Something is definitely not right if you only have 5psi. You say you feel the pump is energizing? If the pump is 'working' disconnect the output line at the pump and run a volume delivery test there. As in hook another hose to it and run it to a container to check the amount of fuel coming out when cranking.

It's a saddle tank system but there is only one electric fuel pump, typically on the right side. The left sending unit is a suction pump using the flow from the electric pump to suck the fuel from the left side and pump to the front of the car.

VoytekC240

John, I replaced the fuel pump today and the engine started and runs perfect. Issue solved and thanks for your help!

My P0400 unfortunately came back but this is separate story.

Thanks!

Mountain_Benz

Same stuttering issue on take off on my CLK500 which was embarrassing and sometimes dangerous. Stalled it twice. Once accelerating on full throttle it was as smooth as butter.

My codes were all good. Cleaned off the MAF sensor to start with, no luck.

Then ran a bottle of injector cleaner though it and now rough idle on take-off is gone.