pwd72s,
thanks for the input.
its a T, and i dont know what all has been done to the car from the previous owners.

brant

I wish I could tell ya, but the car is in storage right now about 4 hours away and I can't remember the part number.

Re-reading carefully, I see you are using Bosch platinum tip? You mean the roundish insulation with a tiny wire of platinum mounted flush? If so...trash 'em.

T77911S was right about the copper plugs. The S models called for a Bosch platinum tipped model that is no longer made, but it was of conventional design...and a pretty cold plug, IIRC. Platinum plugs were originally suggested to help prevent fouling, but with a properly functioning Capacitive Discharge ignition system, such as the Bosch original unit, not really necessary. Copper plugs work fine, perhaps better, with more frequent changes.

MFI cars tend to run rich, even when the MFI is tuned correctly. Are your MFI throttle bodies still tight? Bushing wear in the MFI can cause air being sucked in, making the fuel/air mix crazy...or, if a previous owner (or incompetent mechanic) messed with the MFI in a bad way, problems arise.

(edit again)...I sent Grady Clay a link to this thread. If he posts, you can consider his words as golden. :)

thanks brant. when you get to the extreme end of the heat range, especially the cold end, they can be VERY picky. a car may run fine on W5.6,or 7's, but for a stock car, something outside this range may cause problems. i have been testing heat ranges in my car. i just took out a set of W4's. although i had no problems, i would not recommend anything below a W5 for a stock car. your case is kinda strange in that most people tend to run TOO HOT of a plug, me included until i did research and testing
check the mixture/richen, then put in a W5. the reason i was thinking lean, if it was rich, you would be fouling the old plugs.

go here and read the long post i posted. this is not my opinion, most of this came off the NGK site.


http://forums.pelicanparts.com/porsche-911-technical-forum/438979-anyone-tried-bosch-w6dc-plugs.html