Barry Smith

I have a 1995 C280 (in line 6 cyl) and occasionally this drops to 5 cylinders and the Exhaust temp light comes on. Have replaced the three ignition coils. Also new spark plugs. Also replaced the oygen sensor and the air temparature sensor. Occasionaly the problem manifests itself if I brake very suddenly(severely) when going very slowly. Any thoughts please anyone.

jc723

im going to jump and say engine wire harness??

Barry Smith

Thanks for that - was going to be my next "replacement".

jc723

where are you getting it from? btw which plugs did you use?

PhilfromPA

Just to check, you replaced the coils & the coil end plugs as well?

c280_nz

play with all the wires that go to the injectors also,
i had a loose injector wire and it did the same thing,

imo you changed way to many parts, the coils are twin spark so its normally either 2 cylinders working or not, and if you had just bought one coil and lead you could have changed them thru all 3 positions to see if that fixed the problem, maf sensor and air temp sensor wouldnt cause this.
to fire you need air and fuel, do you know what cylinder it is on? and are you sure its only running on 5 and not 4? if its 5 then itl be an injector wire you may be able to fix *carefully* without ruining all you wires,
if its 4 then itl be ignition wiring,

Barry Smith

Thanks for all the replies people. I am in New Zealand.

The plugs were supplied and fitted by the Service Agent - as were the sensors and the coil packs. Because this was quite an intermittent fault agent said was probably a coil breaking down and he had experienced this before.

The agents used their analyzer and according to them the changing of all these components was the "cure". I have lost faith now!!.

Thanks for the tip on injector connections - will check.

Also because the wiring loom does show some sign of deterioration around some of the insulation, will try that if injector connections do not cure.

99MBSport

You replaced coils and plugs...what about the spark plug wires?? Could be a simple wire problem.

c280_nz

yea could be a wire,
god i wouldnt want to pay that dealer bill!
im in New Zealand to, pm me ur phone number if you want to talk,
like i said, if its not a ignition lead, then it has to be an injector wire.
if its down to 4 and not 5 it will be a coil wire.
if its 5 it will be a injector wire.

i have a few spare coil wires and injectors if its a blocked injector,
how mechanically minded are you?
i totally reckon it will be a degraded injector or ignition wire tho.
and if your confindent you may be able to replace this wire, before taking the plunge into a possibly $600+ wiring loom,
if you want to change the loom yourself i know where a write up is on how to do this yourself
from logan

docd777

i work at a dealership in south africa and we had a w202 c280 in just for service. the car was due for plugs se we changed them. before the change i did notice that the car had the ever so slight miss every now and then while idling. after the plug change the missfire appeared. the cause is from the engine wiring harness wich becomes brittle. and believe me the price of parts are expensive. a good auto elect might be able the repaire if they want to tackle that job. would be alot cheaper

Barry Smith

Thanks to all who replied regarding my problem. For anyone interested the problem has been cured by removing the number 6 injector connector (electric), cleaning the contacts and then simply refitting to the injector.

This has totally repaired the occasional "stumble" I had when at idle and of course no more dropping down to the 5 cylinder mode. If anyone experiences the same type of problem strongly recommend checking injector plugs first.