Hi,
I purchased a 1999 ML430 in December. The past 2 weeks it's been having occasional misfires and when I took it to the auto parts store the code read random misfires. Today I was driving on the freeway and all of a sudden I had a loss of power and it wouldn't go over 60mph. I took it right to an auto machanic and he diagnosed 3 things; the mass air flow sensor, 2 O2 sensors and 3 ingition coils are bad. The total bill they want to repair all of these things is $2300. I don't have $2300 so I was hoping someone could give some advise on how to fix ourselves? Thanks!

 

Do you know what the DTC codes are? Is your CEL "ON"?

 

first off no need for all that stuff yet. make sure your cats arent clogged common issue with MLs.
you might have those codes in the car but that doesnt mean they all caused the problem you are currently having. you proably coiuld use some new coil packs but not likely. they very rarely go bad.
you most likely need spark plug wires first. common problem too.
and o2 sensors usually wont cause the car to not go over 60mph. a clogged catalyst or possibly a bad air mass sensor could do that.
check to make sure your exhaust is free flowing . clogged cats can cause mifire codes and can basically choke your engine.

 

I would go with Chassis221 and that's good news for you vs the $2300.
Start with the spark plugs, plug wires and MAF sensor. Been searching ebay for MAF sensor (Bosch 0280 217 515) for my ML320 and they cost around $100 with warranty.

You can DIY replacement of these parts easily. For the O2 sensor, u would need a special tool due to the tight space to work on.

 

The CEL has been going on and off for the past month. I do not know specifically which codes are coming up. All of the spark plugs and wires have been recently replaced. We are going to start with the mass air flow sensor and will definitely check out the cats. Thanks for all the advise!