C240 112912 engine code emergency help needed!
 

my dads 1999 45k mls C240 with 2,6l 112912 engine has recently developed a strange problem. when you hit the accelerator hard the check engine light comes on and the engine loses power like it is not running on all cylinders. this stumbling goes away when we stop and restart the engine(however the check engine light stays on). our indie took it to MB to read codes and and it threw every code from plugs to coils, O2 sensors right side, brakeassistant and so on.....so MB wants to start with coils, but the engine is running fine as long as you don't push gas too hard... what about cat? only cylinders 1 3 5 have problem. anybody out there had a similar problem? where should we start????
cheers,
reinhard

Most common problem is a VERY lean mixture under load, fuel presure problem(filter) or defective air mass sensor returning incorrect voltage signal!

Thank you MB DOC.Will check fuel filter and swap AMM with known good one from my recently aquired E240. My 320 Coupe died in the last snow :mad: a neighbour slid into it with his SUV. Will post outcome...
Thank you,
reinhard

swapped AMM with no result. how would i check fuel filter and where is it located??? any other suggestions? could it be one of the cats?
thank you,
reinhard

may want to try the forum at <www.mbklasse.com>

I have a question, when you hit the gas and the engine balks what happens to the tachometer? rpm needle falls to zero immediately or the needle stumbles downward?

when were your spark plugs changed? and the wires - have you checked them with a volt/ohm-meter for resistance.

Is your car running the original battery?

After you swapped AMM did you disconnect the battery in an attempt to clear codes/CEL light?

Also check for a vacuum leak around the intake; throttle body, manifold.

Fuel injection - you need a manual to diagnose that, but I would do new spark plugs and wires, and if that didn't work would check the fuel injection starting at the fuel filter.

nothing happens with the tach it just showe the speed, plugs changed 10000mls ago, i did not diconnect the battery and it is OEM mercedes.
i have not measured plugs and wires yet. what should be the resistence??
thank you,
reinhard

I don't know how well the HT wires test with ohm/volt-meter, but if you pulled them out you can just see if they are all within a range.

I would set the ohmeter to the R x 100 scale - touch probes together and zero meter. Then touch probes to both ends of wires.

I kind of thought that mercedes diagnostic equipment could find the fault in the ignition if there was one.

May I suggest you try a new crank position sensor.

My reasoning behind this- 2 weeks ago I had a 2002 ML320, 112 engine, If you drove it like grandma, it was ok, if you punched the accelerator, cyl 6 misfired and it shut down the cylinder. It had been to another shop twice for this problem, they had replaced spark plugs, coil, wires and injector for that cyl, and even replaced coil, plugs and wires for cyl 1 as well. When I got it a month later, I tried driving it with the exhaust off, a new air mass, inspected all the plugs again, ohmed out the wires, checked coil signals on oscilloscope, tested spray pattern of new injector, reset mixture and ring gear adaptation, checked timing of engine, removed valve covers and checked for weak or broken valve springs- finally thought what the hell, I'll stick a crank sensor in it. That did the trick, of course it was going to be the last thing I tried.

wanted to take the car to mechanic today- on the way i thought i woul try to put it into limp mode- it would rev fine. two more start and the check engine light is out. drove car for 30 mls and it runs perfect. miraculous self healing????? :P my dad takes a trip today; we will see...
reinhard

its possible. theres a magic number something like if it doesn't see the problem after 40 starts, it will erase the code on its own.

had the car at mechanic- ECU readout now showed crank sensor-replaced.engine is running fine so far. in addition he found a vacuum leak in the break pressure system.
cheers,
reinhard