Hey folks, I finished an receint service check at 100k and soon after, I felt a weird vibration and what feels like a misfiring at around 2500 rpm and up. This feeling is normaly felt on the highway around 75 mph or higher.

During the service check, I installed all oem parts including (FR7KTC) Bosch plugs, fuel and air filter, trans, coolant, and brake fliud flush (done by shop). Once I installed the new plugs, I noticed a differnt feeling at power up. I believe the plugs were gaped correctly.

I must add, that there is a slight squeeking noise noticed at idle (sounds a little bit like a diesel with the windows closed) which I feel, may be a idler pully. I inspected all pully's but found no play; however, its sounds like it is next to the supercharger and the only visual problem, is the fan blade has some play around the connecting nut.

I will remove the plugs and see if that takes care of the problem, but I feel that is not going to help. Any suggestions?

SIDE NOTE: I just reinstalled the old plugs and the engine is much smoother, but I still have the noise from the pullys.

What is the difference betweeen the old plugs and the new plugs. Do they both have the same gap?

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record

Bosch F 7 KTCR are triple electrode plugs.
They ARE the correct plugs for his car and CAN NOT be adjusted.
http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1FU1CD1PL1OJ15M6P1&year=2000&make=MB&model=C-230-002&category=F&part=Spark+Plug

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2007 C 230 Sport.

Both the orginal and new plugs are gaped correctly and look about the same as far as condition. The older one seem to be working better, because the engine is running much smother. It may be possible that one of the new plugs were defected. I purchased them online through "Autoparts Warehouse.com" (FR7KTC), they are the same as the original were.

Other than the power lag I think it is now gone, but the noise which I'm hearing is coming from one of the idler pullys, but I can not idenity which one. Earlier this week, I was thinking that may-be the worn pully would cause some vibration at higher speeds.

I didn't see it in your post, but did you take the belt off and spin each pulley by hand?

No I didn't because I am short on time to put the vehcile down. I will t/s later when times permits. Thanks