Mercedes Repair Questions? Ask a Mechanic for Answers ASAP
Hi Luis, my name is***** first thing I would do is swap the left side coils with the right side coils and see if your misfires move to cylinders 1, 2 and 3. You can do the same with the ignition wires. I doubt you have 3 bad ignition coils or wires but it's possible. It's more likely that your misfires are caused by a bad catalytic converter for cylinders 4, 5 and 6. A restricted converter will cause misfire codes on the left or right bank. Usually the misfire will occur on hard acceleration. You can remove the front oxygen sensor from the exhaust and road test it with the sensor removed and see if it misfires. The computer will turn off the fuel to the misfiring cylinders to prevent further damage to the catalytic converter. When you cycle the key off and on it will reset and run fine until the misfire occurs again. Another possibility is water in the fuel rail. You can drain the rail and take a fuel sample to rule out fuel contamination.
Let me know what you find.
It does sound like a restricted converter. When you get it up on the lift again try rapping on the converter housing with a rubber mallet and see if you get the rattle. Remember, when testing for a plugged converter you first need to be able to duplicate the misfire on a road test then you need to remove the front oxygen sensor from the exhaust so that the exhaust can escape. If the misfire cannot be created with the sensor removed you have a plugged converter.
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That doesn't sound like a restricted converter. It sounds more like a bad fuel pump or a bad crankshaft position sensor. A restricted converter will cause misfires on hard acceleration but it would rarely cause stalling and a no start.