Ledbelly

Hi all,
I have a 2002 E240 W210 with 65000 miles on it and it has a misfire problem.
It runs really smoothly but has a slightly lumpy idle.
If I floor the throttle I get the check engine light and it throws a misfire code for either random multiple misfires, cylinder 3 or cylinder 5.
Once I get the CEL it does run on 5 cylinders but if I switch off and start back up it is fine.
I have cleaned the MAF sensor and tried changing coils ( I have some spares) but it makes no difference.
Any ideas out there?

e350forme

have you changed or looked at plugs? gap ok?
have you put in new ignition wires?

I have done all the basic trouble shooting for my car, and in the end, she still seems to have a "slightly lumpy" idle that I cant figure out!

khomer2

Scan and post your error codes. CEL came on - this means you have codes saved.

kajtek1

I wonder why changing the coils and not the spark plugs?
How many plugs per cylinder the engine has?

fabbrisd1

I would have the CAT's tested - the front cat tends to breakdown - throwing chunks into the rear cat - which cause blockage and restriction on acceleration.

Low mileage W210 are subject to this..

A. Rear cat blockage can cause this accleration/backup/CEL - rubber mallet - tap the rear cat and listen for that debris - you can cut rear cat out - empty the chunks - and reweld back in,

B. IR thermometer with your E running and up on a rack - exit temperature at back of cat "should be" much higher than entrance temp at front of cat

If by "lumpy idle" - you mean pulling towards a braked stop - the RPM starts to drop below normal idle - feels like engine "choking" - then catches itself and goes back above normal idle - then drops/catches itself again - then you need a replacement genuine Bosch MAF from a reputable source which in the UK is a issue who to trust (and pay). UK has all those cheapie China Maf's - cheap but junk really

If by "lumpy" idle you mean no "choking" - then you need to chase vacuum leak... by "age" plugs are due .. MB cables/coils rarely go out unless overheated - but swapping back and forth can identify a bad cable or coil,

Time for a fresh OE fuel filter too.... and clean up your tank with Stal-Marine 308 fuel stabilizer available from UK Amazon

Ledbelly

Thanks for all the replies. I finally got around to changing out the spark plugs and it is now fixed.
I have to say that the plug swap was nowhere near as bad a job as I had been led to believe.

Ledbelly

Oops! Spoke to soon. The plugs and leads have fixed the CEL/misfire issue and it runs beautifully and gas mileage is noticeably better but I still have a lumpy idle.
It's quite bad when cold and just noticeable when warm, in fact it almost disappears after a good run when thoroughly warmed up.
I tried the MAF sensor off my W209 (same part) but it made no difference.
Has anybody got any ideas? Vacuum leak maybe?

kajtek1

Run injector cleaner.
Than do few "Italian tuneups"