I have a 95 C-280 with 168k miles onit and it runs rough. We have had the engine wiring harness, plugs and ignition wires and EGR valve all replaced just recently. The car still hesitates on occasion when accelerating, and sometimes backfires. The tech who worked on it also installed a mass airflow sensor, but this had no effect so it was removed. No codes show up at this time. Any suggestions? The car is in great shape and is worth keeping. Thanks

Did you change these ?

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..and did you use Plat plugs ???

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A Dalton

Are there tehn 3 components per cylinder, i.e. plug, wire and connector? I had the plugs and wires changed at a non-Benz dealership so I don't really know if the connectors were replaced. Is there a good way to tell?

thanks

These go between the coil and the plug , so there are only 3 of them...it is very possible they were overlooked b/c you can not see them until you pull the coils off each plug and they usually stay stuck to the coil.
They are the MOST COMMON failure part for mis-firs on 104 engines with DIS.
and most Benz Techs just routinely change them when they change plugs b/c they are aware of that.

And these engine do not run well with Plat plugs...but that is another
Benz Tech known thing.
I would not expect a regular guy to know either .
Take a look...

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A Dalton

Thanks. The tech who just replaced the engine wiring harness said he did check those components and said they looked fine. At idle, the car's RPM will fluctuate between 500-1000, and when first accelerating it will backfire 2 or 3 times until it gets up to speed. Once over 30 mph or so the car will run fine.

I did have a look at the old harness- lots of broken insulation and frayed wires- a real mess. The tech said we would never be able to fix the problem if we didn't at least replace the harness.

This car is now very perplexing. We hate to keep dumping money in and not getting the problem 100% resolved. I thank you again for your responses.

Then go get the codes.
Resistor connectors can not be diagnoses b/c theylook fine..they are an electrical resistor and a meter/scope does the looking...not the human eye..

Which us why all the TECHS that are BenzHeads know to change the connectors when they change the plugs, wether they look fine or not...that was my point.
Do a Search on plug connectors on Waste Spark [ DIS} systems and you will see why.
However , with you rpm complaint. I would get the codes first, for sure.
If he did that, post waht codes he retrieved.

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A Dalton