iufan4lifeul

Ok, I have no idea what else could be happening. I had a misfire (especially under load) that started about 6 months ago with what I thought and still think was bad gas. We replaced the spark plugs and that solved the problem completely. After 3 months of it running like a champ the car started misfiring again so I swapped the plugs and it ran good until now. The plugs shouldn't be going out this quick. It misfires at a 1500-2500, under heavy load, and 50%+ throttle. Basically, if I am driving at 2750 RPMS barely touching the gas there is no misfire. Obviously it has to do with the plugs since every time I replace them it fixes it.

Another note is that every time we pull the plugs the color of the plugs varies from plug to plug. Some are pretty white (lean), some are darker etc. It is completely random how they are colored. It does seem though that the 2 rear plugs are always lean and those are the ones I believe that are burning out causing the misfire. I don't think the tune is great on the car but could this cause the plugs to foul out that fast? Should I put it back on a dyno and have it retuned? Also I am considering switching the injectors around and see if the lean plugs follow certain injectors.

Any advice is appreciated, sorry for the long post.

OzzDOA

What plugs are you using?

jwog666

is the mil on? if it is, what codes? i have seen this before with a weak coil on plug. i am doubtful that it is the spark plugs. the coloring of the plugs can vary, if the engine is running too lean the pcm will set a code and will add more fuel to compensate for it. from what you describe i would focus on the ignition coils.

WhiteFoxGT

What cylinder is misfiring?

Does it throw a code?

WhiteFoxGT

you beat me to it by like a minute

I was basically going to say the same thing.. A weak coil can cause multiple misfires... The RF and whatnot will just freak the other coils out as well.

iufan4lifeul

No codes are being thrown whatsoever. I am using motorcraft plugs (just the ones that you get at autozone when you ask for 2000 gt spark plugs). I am just confused why would a COP cause the car to run for 2-3 months PERFECTLY and then miss until I replace the plugs. When the plugs get replaced the problem immediately goes away. I did notice that on some of the plugs the 2 wires on the harness going to the COP's have the wire exposed just a bit (cracks in the insulation). I electrical taped them up really well but I don't think there is really any way to fully replace those is there?

WhiteFoxGT

The only right way to go about this is to do a powerbalance with a scan tool and actually see which cylinder is acting up, then go from there

WhiteFoxGT

Weak coils can foul plugs

jwog666

+1 whitefoxgt

iufan4lifeul

Can you elaborate on this please? How do I go about determining what cylinders are misfiring? I have an Xcal 2 (I think) that is used to tune my car. Can this tell me or will I have to hook it up to a more sophisticated diagnostic computer? Say it shows 2 cylinders misfiring... Would you all recommend doing new plugs/COP's for those cylinders and going from there?


Chris