W124 280 Misfire

[GP801]

New to the forum. I have a 1995 E280 estate, 129,000 miles. The problem is an intermittent misfire. Twice it has started to run as if missing at least 1 or possibly 2 cylinders. On both occaissions this suddenly cleared itself and it ran perfectly for the next few weeks before recurring. There are receipts from the previous owner for a new wiring loom and coil packs last year - fitted by the main dealer. Had new fuel filter 2 months ago when last serviced - again main agent.
I would like to know how likely is this to be the dreaded loom or coil problem given the recent new parts and would it only cause an intermittent problem. Fuel is usually shell or other reputable source.
What else should I be thinking of?
Despite this problem the car is one of the best I have ever owned. Brilliant long distance comfort and everything works as when it left the factory - roof, aircon, elec seats etc.
Many thanks in advance for your help.

 

[grober]

Time to "inspect"the new coils and wiring loom? There can be problems with the extender plugs from the coil to the plugs-possibly not replaced with the other HT stuff? items 8 and 89 here. çàï÷àñòè Mercedes: êîäû çàï÷àñòåé ìåðñåäåñ and treat yourself to some NGK plugs http://www.ngkpartfinder.co.uk/
ps were all the coil packs replaced?

 

[Ian B Walker]

The rubber extensions under the coil packs do break down after time. If they are old and for about £15 it may just be worth changing them.

 

[tobyd@callnetuk]

This sounds like the problem I had with my E280. It had a wiring loom issue and that also caused damage to the ECU which got worse and had to be replaced.
Hope that your problem has a cheaper solution.
Toby

 

[GP801]

Thanks to everyone.
There are receipts for all the coil packs but I dont know about the extenders. This seems worth a try and not expensive.
I currently keep the car in Italy although uk registered. At least labour rates there are much less than in uk - 50euros/hr main dealer. Will be interesting trying to explain it too them.

 

[kth286]

even with a new engine wiring harness (loom) ask anybody working on the car to avoid bending the coil feed wires.

you do not want a set of cracks in the inner insulated wires to short to each other and cause major problems.

 

[Dave Lewis]

.....At least labour rates there are much less than in uk - 50euros/hr main dealer. Will be interesting trying to explain it too them.

If you're taking it to a main dealer (50 euros ph is cheaper than a lot of UK indies) get them to read the fault codes first off. This will help identify where the problem is. As already said, the plug connectors under the coils are possibly suspect, along with the other 3 plug wires and connectors, and whilst doing that, new plugs of exactly the right spec should be fitted as well.