Mis-Fire

[mercman1969]

Will a CPS cure a mis fire?

Took my W163 to an independant last week with a huge mis fire

They said that the CPS was showing as intermittantly faulty and changed it

Drove it back and told me it was all done

Not convinced as car seem to still be the same?

Gearbox is still not kicking down 100% of the time and only seems to do it when it feels like....not ideal if overtaking

 

[grober]

I don't recall Crankshaft position sensors causing misfires-usually engine just goes dead but who knows? Did they mean camshaft position sensor? If you still have the misfire problem I would be looking at the high tension side of the ignition.

 

[benztech]

Bull....!!! Crank sensors only ever fail and they cause the engine to start. Recognition sensor to signal the sparking of the plugs they do not or can not cause a misfire!
These engines require spark plugs every 60k but if it has been done it is probably the leads or a coil pack.
I suspect these are your first steps are their any faults or have they checked????? their would be evidence

 

[PJayUK]

MAF Sensor?

I have had a very strange intermittent issue with my S320, lumpiness & missing in fact it sounded like a london taxi.

A quick clean of the maf sensor and its running smooth as silk again, I plan to change it later this month but so far a clean seems to have helped.

I have heard that MAF's cause some very strange problems.

 

[BlackC55]

CPS will not cause missfires.

Where did you take it?

 

[mercman1969]

It has been into MB Nottingham - an independant

they had it for a service and to replace the spark plugs as it is running LPG and ignition is critical

It has not been the same since which led me to think coil packs or leads

Gear change was also lumpy so took it back and they flushed and changed the oil......no real big difference

Took it back and they called to say they had changed a sensor that intermittantly flat lined and was subject to a STI from mercedes

Delivered it back saying it was fne....1st test drive i took it on exactly same problem....called them and he told me it soundedl ike the gearbox needed replacing at a cost of circa £4k

At times....and only at times when you grab a handful of throttle the revs will rise sharply but the drive isnt taken up, but follows eventually

Sure it is something very simple to cure but I am getting to the point of just wanting shut

Car is used to drive my 3 year old to nursery by my wife who isnt the most confident of drivers....it nearly killed them 2 weeks ago when it coughed and spluttered whilst crossing 2 lanes of the A1