I had noticed my car not responding as well recently. When coasting at around 40pmh, if I openned the throttle wide, the car would hesitate to speed up. Also my car was running very sluggishly, vibrating in a word. What I had previously believed to be a fuel filter related problem, turned out to be my spark plugs that I had replaced when I bought the car with NGK TR5GPs. This was last July (2004) I have driven about 30K since. Well I figured I might as well check out the plugs, turns out that plugs 3 and 6 and a lot of gunk and seemed oily. While the others had little or no gunk and werent oily. They were dry and had a greyish residue over them.

Well I replaced the plugs with Bosch platniums. And the car responds a lot LOT better to sudden acceleration.

I am just curious why only the plugs from cylinder 3 and 6 were dirty and not the rest?

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190e 2.6 1990. 300,000 KM
C230 K 2000, 130,000 KM

You 'may' not want to find out. Could indicate valve problems .... among others

cheers, guenter

I would consider using non plats. The spark on the plats isnt that big and that could lead to your fouling problem.

The plats are a no-no. Use only what the owner's manual suggests.

Your fouling problem will eventually return. The rear most plugs are fouling first, no?

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'90 300SE 298k
-300K and it gets put into retirement.
'80 300D 255k Purchased new by family in 1980.

Had a:
1973 220 (gas)
1980 300SD
1992 400E

YOU SHOULD NOT USE RESISTOR PLUGS ON MERCEDES!!! The ignition system is very carefully designed for use with non-resistor plugs. Resistor plugs add secondary resistance is excess of design specs and alter the secondary voltage wave form.

Sooner of later you will have problems such as rough idle or high emissions.

The proper plug is Bosch H9DC (NOT the HR9DC resistor type), and these are not commonly available at McParts, but are readily available for two bucks each from Mercedes parts specialists like Fastlane, which sponsors this site.

Any spark plug with an "R" in the designation is a resistor type and should NOT be used.

Duke

Ok understood, I changed to non-R type I believe but I will double check.

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190e 2.6 1990. 300,000 KM
C230 K 2000, 130,000 KM