Hi Everyone,

My 97 E420 suddenly had rough idle when in "D" after I washed the engine. It was also rough in Newtral. The Engine was quite warm when I wasked it. I let it dried completely and then I started the engine. It was running fine until it warmed up to operating temperature.

I noticed that there was a sticky smell like rotten materials. At one point, engine would not start after it shut off when idling at stops. I had to let it cool down and then it started again. As soon as it got to operating temperature, it ran very rough and it would shut off when idling in D and/or Newtral.

I did some diagnostics and found water sipped into the spark plug holes when removed the ignition coil and the boot. I let them dry and it is working working better. The only problem is now that it would idled rough when it is in "D" but not in "N". When the RPM exceeding the the 1000 RPM, then the engine ran fine. Scanned engine and it showed that #3 and #5 are intermittent misfired.

Questions:

1/. What is the cylinder numbering and firing order for the 4.2L V8 engine?

2/. If there is a problem with the ignition coil (3,5), why did the rough only happened when it was in operating temperature and only in "D"?

3/. Is there any problem with coolant temperature sensor? I could not find it on the engine. Please help with part number.

4/. Is there any problem with Crankshaft position sensor? Would it damaged with water?

5/. Do you think that a bit of water or huminity can cause the ignition coil unit to malfunction?

Thanks in advance for any help!!

W

 

answer to #2 is at idle it has no load on engine and the other 6cyl are fiiring so it souunds ok,put it in gear and you now feel thee lac of 2 cyl.on a 4 cyl motor you will feel one dead cyl,even at idle speed.