Hello

My 02 f150 5.4 is misfiring. By reading through your forums (these pages are great) I belive it is a COP problem or plugs. I just assume that I replace all the plugs and the bad COP. My question for the experts is if I get a code reader, I saw one at my local autozone for $30, will it tell me which one I need to replace or just that I need to replace one and I have to fugure it out on my own?

Thanks for any help!

P_F

 

The code reader should tell you which cylinder is misfiring. For example, if the code set is P0301, that means #1 cylinder detected misfire. Any Autozone will read the codes for free, if you don't want to invest in your own reader.

However, just because you get a misfire code set DOES NOT necessarily mean that the COP is bad. It just means that something in the ignition for that cylinder is not performing well. Could be plug, could be COP, could be the boot between the COP and plug, etc. On the Tritons, I have myself found a bad boot rather than the COP to be the culprit---about $3 at the parts store.

The Haynes book for this truck includes a test procedure for COPs, testing the primary and secondary resistance with an ohmmeter. But, you can also narrow it down with the substitution method---just swap the COP indicated by your misfire code with another COP, then see if the misfire code "follows" the COP, in other words, does the P0301 now become P0302, for example. If it does, then by substitution, you have eliminated several sources of the misfire, and narrowed the suspicion to the COP.

Hope you find that your misfire is NOT P0304 or P0308, which are the most difficult cylinders to reach on the Triton.

 

gibsonj, thanks for the reply. Great info. I will post my results.

 

It turned out to be P0306. It was the COP. Swapping out was quick and easy. I can't imagine the time 04 or 08 would have took. Also, a day before it develped the misfire, the remote started to have problems. It would mostly lock fine, but would unlock sporadically. I assumed the batteries in the thing were going, but as soon as I changed the COP the remote went back to normal. Could the COP have had a short that caused this? Coincidcence?

Thanks again for you help!!!


P_F

 

Well, I'm assuming that your truck was not running when you were trying the remote. If the truck were running, then I guess there's some small chance that a malfunctioning COP could be giving off EMI that could compromise a remote's transmit frequency. Pretty unlikely, though, in my opinion.

Otherwise, the on-board computer modules that control the COPs and the remote functions (door unlocks, etc.) are different modules, so I would not expect any cross network relationship between a failing COP and remote functionality. You don't have an after-market remote start module installed, do you?

Maybe someone else will have an idea. I'm pretty much out of my league with this one.

 

No, it came right back. I think it is the batts in the keyfob. Thanks again!!!

 

I thought I was home free, I guess not. I went out for lunch and it started to misfire again. Not nearly as bad, and it went away after about 5 minutes. I think I will invest n the scanner and see what is going on.