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unfortunately I've been having a problem with misfiring in my 5.5L M273 on cylinder 2 for a few weeks now. The code in the fault memory is P0302. When I look at the misfire count in Xentry, all cylinders besides cylinder 2 have 0 misfires, while cylinder 2 is misfiring strongly. The check engine light comes on and sometimes flashes, after which, as far as I know, the injection of cylinder 2 is switched off so that the catalytic converter is not damaged by the frequent misfires. I notice a rougher running after the engine control light flashes, and I can feel that the second cylinder is not running anymore. When restaring the engine, everything is back to normal, check engine light may turn of or stay on.
These misfires only occur when the engine is warm. If I start the car cold and leave it until it reaches 70 degrees +-, the cylinder does not misfire. The misfiring also only occurs when the car is stationary. When I drive 500 km on the highway, I have no check engine light and the vehicle feels like it has full power. If I stop at traffic lights for 30 seconds after driving even long distances, the check engine light may come on and/or flash, but only sometimes. It also happens that I can drive in the city with lots of traffic lights without an engine control light.
However, if I shift the transmission to N or P at a red light and keep the engine speed at 1000-1500 rpm, the misfiring and the check engine light do not occur either. I have therefore already tried in Xentry to set the engine idle rpm to around 900 rpm (maximum) and to adjust the ignition in the early or late direction (via Xentry), as well as to inject more or less fuel ("rich" or "lean" injection via Xentry), but none of this has helped.
I have already swapped the ignition coil, spark plug, injector and the injector seals. I have also replaced the intake manifold and throttle valve gaskets, and checked the wirings and spark plug connector. Two years ago, the previous owner replaced the intake manifold with a new one from Pierburg. Plastic parts had broken off the old intake manifold and damaged the valves of bank 1, where the affected cylinder 2 is located. In the course of this, the cylinder head of bank 1 was overhauled and the valves replaced. The timing chain was not replaced because the timing was good. After the cylinder head was overhauled, the car ran smoothly until a few weeks ago.
The car has a mileage of approx. 250,000 kilometers.
I suspect an electronic problem, possibly with the ECU, as I've read either on this or another forum that someone has had a similar problem with M273 or M273 engine.
My question is, what is the best way to proceed to find the fault? Does it make sense to have a compression or pressure loss measurement carried out before sending in the ECU for costly repair, or are faults in this area unlikely with my fault pattern?
Cyl 2 spark plug was oily, the seal between the valve cover and the spark plug appears to be leaking a little, but this is unlikely to cause misfiring (even after swapping the spark plug and coil), is it?
I thought I'd post this here on this adjacent topic rather than creating a new thread. I'm putting in new fuel injectors in my M273 using new Standard Motor Products injectors. Of the eight I bought, four are missing the top brass colored port. I've not done this job before, and don't know what to make of it, other than that brass port on the OEM old ones and four of the Standard new ones is probably important. I watched an FCP Euro video carefully, and it appeared their parts on a Mercedes video also did not have the port. Can anyone clarify what it is, and confirm it should be there? The Standard part numbers were all the same and otherwise identical.
those links to the inlet trumpet switching are so well hidden....
check the solenoid valve - left front down by the dip stick tube - you can also get a tube and suck on the three diaphragms in your picture to try and see if anything works
@nath h, what did you do with those injectors - bought normal ones ?
M273 Cyl 2 Misfiring
