MFI-What Color Should My Spark Plugs Be?
 

For those of you that have your MFI dialed in, what color are your spark plugs? I know the MFI runs rich, but do you have any black dry soot on your plugs with just a clean area on the electrode? Can they be read like on other fuel systems, that is by color on the tip?

Kurt V
72 911E

On my 72, it depends on how hard i drive. Sometimes when I pull them after city driving and traffic, they can be a little sooty., Drive it hard and they are a nice shade of brown. But, not all the plugs look the same? Some of them can be more sooty than others. I don't foul plugs with bosch super plugs. I run my pump rich.

what kind of plugs do you have (MFG & model)? the PO had a colder set of plugs than stock, and once i replaced them with stock NGK's, and fixed a broken heat exchanger-to-thermostat hose, i stopped getting sooty plugs and got nice brown ones.

i'm in the process of dialing in my MFI as part of my tune-up process.

[QUOTE]Originally posted by lsolon:
I don't foul plugs with bosch super plugs. I run my pump rich.

What is the number of the plugs you are running and what gap are you using? Thanks!

Kurt V
72 911E

TMC: Thanks for the response. I'm running NGK BP7ES and the thermostat is working fine. I'm still fiddling with the MFI Idle and Main mixture settings. All other settings are set per the "Check, measure and adjust" manual.

Kurt V
72 911E

The bosch plugs are:Bosch super, W7dtc. They are the 3 electrode type. Gap is already set. I think they come in 6, 7 and 8 heat ranges. When I went to these plugs, they cured allot of my problems with fouling other plugs. They are about 6 bucks a piece. They work great for me. I have been using them for about 6 yrs now.

Uh, my spark plugs are mostly white with green lettering. Silver at the bottom of course.
regards,
jlex.

My plugs are usually on the light side sometimes bordering white and the car runs fantastic. I've been fiddling with the MFI for years and my car runs best at these settings especially in A-Xing where low and midrange is most used. Believe it or not I use AC#4 rapid fire plugs and seem to work better than any other brand yet.


Kevin Kipta
72 911T/E