65vette396

Hey guys new to the forums and just thought first off I would say hello. Next, I purchased a 2000 ML 320 through an auto auction (My father is owns a used car dealership). Well, the vehicle originally wouldn't shift out of first gear, took it to the local MB dealership and they serviced the transmission, now it shifts fine. Next problem we have encoutered is that it has some rattle coming from the engine area, although I do not believe it is internal as it is intermittent and the engine is perfectly quite when you rev it. This rattle generally occurs when there is a slight load placed on the engine i.e. initially when you put the vehicle in reverse or drive from park or nuetral, or when you turn the streeing wheel all the way to the left or right and the power steering pump puts a slight load on the engine. Next and final problem is the vehicle keeps throwing a code, which in turn causes the vehicle to freak out and miss on several cylinders (Have an OBDII scanner, always the same codes). The vehicle will run fine for a while and then the check engine light will flash a couple times and then stay on and the vehicle immediately develops a horrible misfire( like it's running on 3-4 cylinders). If you turn the car off and restart it the misfire will go away, but the MIL light stays on. Then it will randomly start the crazy misfire again at another random time. This happens even if you clear the codes . The codes it is showing are: Cyl. #2 misfire, Cyl. #4 misfire, and Random Multiple Cyl. Misfire (Once it showed Cyl. #1 misfire, but generally it is only 2 and 4). I will be putting the vehicle on the lift tonight and just wanted to know if anyone has any idea as to where to look. I read about the harmonic ballancer (figure that might be the rattle), so I plan to check that out. We already changed the plugs in the vehicle, so I know they are good. Does anyone know how MB senses a misfire??? I mean does it use the knock sensor??? If that is the case it may be picking up a misfire due to the rattle I am talking about. Once again, the car does not miss at all until the MIL light comes on, only after that. Any help would be greatly appreciated, as we already took it to the local Dealership and they said it was fixed (all that was done, was the codes cleared). Thanks in advance, Drew

mbtech75ny

if you a computer to scan the car with you might want to check the mass air voltage with the key on not running if its 1.03v and higher the mass air is bad. it does not set a code all the time, mas air sensors can cause misfires. I see you replaced the plugs, go and replace the suppressor wire on those cylinders. also check the crankshaft postion sensor, located on drives side on transmision bell housing ohm out new one is 600 ohm, if its over a 1000 replace it. good luck

65vette396

Thanks for the help, got it fixed. Mercedes dealer neglected to check anything mechanical. Pulled the inspection plates and all of the torque converter bolts were loose. Tightened them all to spec, no rattle no misfire code. Took all of about 15 minutes including putting it on the lift. Drew