W202 ?? C280 Straight Six Misfire

[Phantom Mark]

My fingers and toes are crossed for the plugs sollution !!!

When you mention the "boot" to which do you refer ? the big plastic/rubber grommet bit which plugs into the top of the spark plug ?

[momomo]

Originally Posted by Phantom Mark

My fingers and toes are crossed for the plugs sollution !!!

When you mention the "boot" to which do you refer ? the big plastic/rubber grommet bit which plugs into the top of the spark plug ?

Yes those are the ones, they are referred to as boots.

[Phantom Mark]

Ace thanks mate, I think I will pop into GSF today and see if I can get a lead set with "boots" as well as the plugs then, no point being half prepared

I noticed in the service history that they have failed to fill in the coolant flush tickets, is this gonna be an easy enough job to do at home ??? I know on many cars this car be a royal PITA because of air locks etc ??

[w124coupe]

I would get the boots from Merc - only a few quid and only 3 of them - they are critical on this engine and I'm not sure pattern parts would do the job.

The lead set is expensive and may be OK.

Try plugs and boots first?


Re the coolant, its easy enough to change (leave the heater on full). Make sure you get the right spec antifreeze (or buy from Merc) as the car has a mix of metals and plastics and needs the right (50/50) mix.

Do the thermostat at the same time as changing it loses quite a lot of coolant (or needs it drained first).

There are two drains, one on the bottom of the radiator and one in the engine block on the drivers side low down. You have to drain both if you want to change all the coolant....

[Phantom Mark]

Well here is an interesting update.

Bought some plugs today, could not get Bosch so I got NGK BCP6E

All the plugs in general looked quite rich IMHO with a small amount of depositing.

Plugs 2, 4 and six, the "boots" were wet, quite possibly some water ingress from the damp, however all of those plugs were soaked in fuel as well, where 1,3,5 were all dry, the car had not been run at all today before starting work on it.

I cleaned up the boots with a rag before refitting the new plugs, and sprayed a healthy dose of carb/injection cleaner into the throttle body, the flap itself looked pretty clean I must say, I also emptied a full 250ml treatment of STP injection cleaner into the fuel tank (which is roughly quarter full atm)

Refitting and check securty of the cross pipe and maf etc and struck her up, smoothly idled for 5 mins no problem, washed my hands and took her for a spin, no apparant missing for the first few corners, then when I head up the hill out of where I live I got a few backfarts through the air box as before, it simply does not like heavy load at low speeds it seems.

I headed up the local bypass at a steady 60mph and smooth as silk, at the roundabout at the end to come back again it backfarted a little again, again heavy loads slow speed..........on the way back down the bypass I gave it some, used the kickdown and she seems to pull ok all the way to near max RPM, all the way up to a ton briefly.

Not sure how quick this should be, hard to compare when you look at my regular drive !!! felt pretty ok tho compared to my old 2.5 24v 525i (similar power and torque)

So yes, the situation is improved for sure, but not solved........did not replace the leads and boots today as I was not able to get any.

Feeling pretty confident it is nothing serious anyways, because the car is at least showing it is willing to run properly.

Tomorrow I will aim to get boots and leads, however the fact that the car seems to pull well under full load once the revs are up lead me to believe at least it is not those parts, or even the coils ??? I would expect those to break down the more load I put through the engine ?? Seems we have that but only in a low gear at sub 3000rpm sub 30mph ??? A little contradictory ?

Cheers