Random Miss

[naval-avi8or]

I recently changed the plugs. I found and replaced one coil do to a small crack in the insulator boot. Shortly after doing the plugs I started getting a miss that has progressivly gotton worse. The miss is only apearent at idle up to around 1000-1200 rpm. I have pulled all the plugs and have found no signs of any wet or fouled plugs and the only carbon deposite's are on the very tip of the outer threaded area (the tip/insulator look brand new an all plugs).

The miss is very random sometimes it just last for 2-3 seconds some time it cycles for 5-6 sec quits for several seconds over and over and other times it is nearly constant (rpm drops aprox 100-200rpm). Checked codes with the Xcal and no miss codes and as bad as it is at times I don't know why that even put a code for miss fire.

I have unplugged the coils/injectors and can't seem to find any one that makes a significant difference. I also swapped the coils around to there original position and rechecked with no luck.

 

[NebraskaSHO]

Drive it HARD until it fails completely. Coils like to go bad after you mess around with them, in your case putting in and checking the plugs. I drove for a month with a random miss and drove my card hard for two hours on my trip back home and finally got the bad coil to give up the ghost. Otherwise, just buy four new ones and install in the rear bank. If it still misses, put the old coils from the back in the front.

See my "I hate coil packs thread"

 

[me6894]

or you could get access to a scanner that has a misfire counter and see which cylinder is missing and save your catalytic converter(s)

 

[NebraskaSHO]

True. There is a Ford program called ISD that allows you to view each cylinder and it's power output.