ZW99GT

I'd replace the plugs for >$20 and see if that helps before dropping $100+ on new coils.

cliffyk

Then you're 15k past where Ford says replace the plugs, and 50k to 60k past where I'd say replace the plugs. Changing them will probably take care of your problems...

twin turbo pilot

Hmm im at 60k miles ive been debating changing the plus on my car but it runs just fine, smooth, strong, and still gets great mileage. Ehh why not though just for my own piece of mind. Ill go with the NGK tr6s is it just a matter of unbolting the old ones and putting the new ones in? what about the gap? also stupid question but how does spark plug gap affect the performance or spark plug etc. I would go out and pop the hood on my car, but i wont be home for another 2 weeks.

Aereon

Changing the plugs is relatively straight forward, the passenger side is a bit of a pain.

gtg532u

ngk plugs or motorcraft

brian1570

i'm running motorcraft, and they r good enough for everyday aplications. and also they are supposed to be pre-gapped but i double checked them w/ what the box said. i forget the actual specs though.

gdoc89

Ok...changed plugs...NGK tr55's. Color was good on each but the center electrodes were worn down pretty good. Guess I got full use out of them. Much better, but still some hesitation under load. Changed fuel filter tonight but haven't been out to road test yet. I did find a set of coils on Ebay for $70...so I can swap out if necessary....stay tuned. NPI!

twin turbo pilot

thanks but im still wondering what does spark plug gap affect?

cliffyk

Primarily it affects how much voltage it takes to ionise the gap, and because it takes time for the the output of the coil to reach that critical voltage, it affects timing to a very small degree. Wider gaps take longer to ionise = a slightly retarded (less advanced) spark, though this is not a significant issue at any engine speed our cars can spin.

Normally on an n/a engine it takes 16kV to 22kV to ionise the gap and then 4kV to 6kV to sustain the spark (less at idle, more at WOT), as the gap widens the ionisation voltage increases faster that the sustain voltage--at some point the coil will be doing it can and still fail to ionise the gap, the plug will not fire, and the energy in the coil will dissipate in the coil as heat, or leak through the secondary winding insulation at the point of least resistance.

If this happens often enough the coil may overheat and/or develop a short at that point of least resistance in the winding's insulation.

So, short answer: A closer gap requires less voltage to fire and because of this will have a smaller spark, with less initial energy, but one that is more resistant to "blowout" at higher compressions and cc pressures.

A larger gap requires more voltage to fire, but will have a larger spark with greater initial energy.

twin turbo pilot

exactly what i was looking for thanks