2001 ML 320 3.2L Motor
 

Can anyone help with some advice about working on my car myself. My check engine light came on and took it to the mechanic to check the codes. They read P0300 throguh P0303. He says two of the ignition coil are malfunctioning. he recomende to replace all three and all of the spark plugs. Is it as easy as replacing the coils and spark plugs. Is that something that I can do myself? I looked at the coils and all it is to replace is removing a brace and disconecting it. Does aybody know why the ignition coils ge damaged? Can anybody vewrify that the codes have been properly interpreted by my mechanic.:eek:

Not sure on the codes but coils get damaged by age and use. Your car is 9 years old, and those ignition parts have probably never been changed. Them failing is not out of the ordinary. Plugs are a good idea as they are not good forever and are directly connected to your coils basically causing ignition for the motor to work.

Hey, Alex. You actually have 6 coils and 12 spark plugs on your engine.

Sounds to me like your mechanic is shotgunning it.

Plugs are pretty easy, if you have the tricky wrench to get the boots off., about $25 on ebay. Check the wires for resistance while you're swapping the plugs and replace any that test more than 25 or 26K.

Coils rarely fail on these engines, and when they do it's not all at once. Since all of your misfires are on one bank, it's more likely to be a vacuum leak, a bad cat or a flagging O2 sensor that is triggering the codes. Cats are problematic on your model anyway, in case you didn't know.

But I'd start easy and inexpensive. Change the plugs and test the wires while there (note that there is an a and b plug for each cylinder, that correlates to the a and b on each coil, be sure to match them up, no anti-seize, Bosch 7422 IIRC). Check for vacuum leaks (everywhere) while you've got stuff pulled apart, and replace the breather hoses and reseal the covers (common leak points), too. Take your time and be thorough and that will cost you most of a day, but it's much more satisfying (and cheaper) than shotgunning it.

The open end of a common Craftsman 17mm combination wrench worked perfectly for me.