OK, I have been fighting this problem for a while now. I have a 2000 ml320 .The check engine light keeps coming on with the code for number 4 and number 5 cylinder missfire and a multiple random missfire. When i turn the light off it stays off for several days or until full throttle or rough driving. I have changed the plugs couple of months ago but i put bosch platinums +2. I think that the wires are still original ones. The car has 90K on the clock. Please help I don't know what to do any more. thanks in advance.

Switch the wires from the affected cylinders to unaffected cylinders to see if the problem moves with the wires. If it doesn't, move the coil packs from the affected cylinders to see if they are what is causing the problem. You should easily be able to locate the problem using this method.

Exactly what i was thinking, but the bad thing is that the light wont come on or at least not instantly. Anyways i'll try that and I'll try to get on it maybe it will trigger the light so i can read the codes. thanks

oh yeah, which ones are 4 and 5 cylinders. Is there a diagram here that i can find or link to one. I would appriciate.

The cylinders are numbered from the grille to the firewall on the passenger's side: 1-2-3 and from the grille to the firewall on the driver's side: 4-5-6. There's a diagram on here somewhere. Something like (< = front)
< 1-2-3
< 4-5-6
If that makes sense?

I would not be surprised if it is the +2s causing the problems. If you search this forum you will find all sorts of stories of people using +2s and +4s and having misfires, then when they switch back to the OEM style plug form Beru or Bosch, the problem disappears. If the problem was not around before the plug change, I think we found the issue.

The OEM plugs are expensive (around $9 a piece) but worth it in terms of lack of headaches!

Even less of a headache are the OEM ones in the ML320CDI!

__________________
1973 280SE 4.5 (Sold)
1984 LWB 280GE (Sold)
2000 G500 NMLE - "Deep Throat"
2007 ML320 CDI (Sold)
2010 Porsche Cayenne S Transsyberia TipTronic (Sold)
2010 Audi Q7 3.0 TDI (Sold and Sorely Missed)
2014 ML350 BTC
2015 Audi Q7 3.0 TDI (On Order)

ok, thanks guys. I am going to switch the wires and surely get the new plugs. My concern is if there is anything wrong with the cats, i while back i had to change one of them under waranty , that happend b/c of the mass airflow sensor. Now the waranty expired and i read some stories about bad cats with almost the same symptoms as mine. thanks