Just bought an 01' ML430
P0300 - Random/Multiple Cylinder Misfire Detected
P0306 - Cylinder 6 Misfire Detected
P0308 - Cylinder 8 Misfire Detected
O2 sensors doubtful. I am leaning towards fuel delivery or the MAF.
In the fuel delivery area it could be a pump/filter issue. Possibly an
injector, but I doubt the injector based on the random misfire code P0300.
If the fuel pressure is not constant there will not be enough going to the
affected cylinders to allow detonation in that cylinder.
The MAF can make them do this. The darn things usually show fuel trim
codes along with misfires, but they do show a bad MAF code. That always
drove me nuts on the 430 engines.
If it were me I would get a good indy to do the fuel pump (you need
that to get the fuel gauge working anyway) and the fuel filter.
Also have him use a scanner that can read MB specific codes. The
scanner Advance uses is generic and will not show most of the MB
specific codes.
Even a bad load of fuel can cause these problems. Misfires like this on any
make or model can be a real goose chase based on all the variables the
fuel delivery system has to tolerate.
Also the random BAS/ESP light could very well be a $15 brake light switch
that is also a very easy DIY job.
It is worth the try to fix the BAS/ESP because a large amount of MLs
have had this switch go bad and cause BAS/ESP lights to come on.
If the switch does not fix it a scanner that reads the MB codes for this needs
to be used. I have seen wheel speed sensors also cause erratic BAS/ESP
codes.
Again a cheap part to replace easily. I just hate to throw parts a vehicle
without knowing what is causing the problem.
Also do we know when the plugs were changed if ever? I have seen more than
a few MLs over 100k miles with the original plugs.
If it is the MAF it is a ten minute job and the part is DIY. Price for genuine
Bosch should be around $150. The dealer will rape you on this part.
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