right spark plugs finale

[shangoof]

correct me on this matter if am wrong,good reference for future searches after doing some research on the forum, my understanding was not to use resistor spark plugs and stay away from platinum plugs. so i called the dealer and they said that the right plug for 1994 e320 is bosch f8dc4, contacted fastlane (peachparts.com) they confirmed it and gave me a code to search for on the website as the f8dc4 doesn't show up on there, limited supplies, so i bought them changed the old ones which were bosch fr8dc+, the car was running fine for 20k miles since i bought it, lately its been losing power so i thought spark plugs are due when i put the f8dc4 the car had severe hesitation from start, checked MAF and everything seemed in place. so i put back the old plugs (fr8dc) and car went back to normal so the are the f8dc4 made for the m103 (300e from 1986-1992) and the fr8dc+ made for the m104 (1993 300e and e320 1994-1995) wiring harness has been changed

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[i6h000]

The f8dc4 is the correct plug for my 92' CE (104 engine). This is a gasket type plug. I believe the 103 engine uses a taper type plug (no gasket). Check it out, don't put a gasket type in the 103, not only will it not seal properly but it won't extend fully into the combustion chamber. The last few threads for the spark plug will also be exposed to the comb gasses and will get burnt and fouled w/ carbon. When you do put in the correct plugs they will be difficult to screw in all the way and seat properly. I been through this with a friends car, (90' 300E, 2.6, 103 motor).
Mike

[RBYCC]

M103-12V used discontinued Bosch H9DCO plugs.
IMHO best replacement is the NGK BP5EFS or one step colder BP6EFS.
The M103-12V used a taper seat plug.

Ed A.

[shangoof]

thx for the comments
i will try the f8dc4 plugs again, maybe i screwed up something
its just that for 20k miles the car ran fine all that time with resistor plugs
i'll keep you posted

[shangoof]

so i finally got to try the plugs again today,
and let me say DAAAMN, the car never drove this smooth i couldn't believe it.
so i dont know what i messed up the first time but i did clean the anti seize of the plugs after reading some comments about that, maybe thats what it was
thank you all for your help
and RBYCC, am glad your on this forum, i read all your helpful comments every where i look on the forum