I have a 2002 f-150 that sometimes has a miss upon acceleration but not all the time.the truck is a 4.6 with a manual trans.has no engine codes and scanner never show a misfires but sometimes it does , have replaced all spark plugs and coil boots twice.anyone ever had a problem like this, need help!!

 

resurrecting the dead,,, anyone have a fix for this??? Ive replaced the coil pack n plug. but the misfires count up as the engine is put under a load. No misfire codes. but the computer shows misfires. thanks guys

 

No idea of your truck and its history, but I had a 2000 F150 with the same motor years ago with a similar problem and what had happened to mine was it had sat for years without being driven before I got it and a small amount of water got down into the bore around the plugs somehow and rusted/pitted the cylinder some and was the cause of my issues. You might try pulling the plugs and having a look as I replaced all the plugs and packs before I finally found the cause. The cylinder on mine that did it was the #7 i believe (the one at the very back on the pass side right under the firewall).

Aside from a wiring or computer issue somewhere else causing your problem that I don't know about (most of my knowledge is 96 & down trucks) its worth a shot as it happened to me once.

 

IF all is good plugs, COPs boots....dry spark plug wells...then make sure that the COP connectors are getting seated correctly or completely. Also note if one of the spades in the connector is bent or loose.

then make sure the relay for the ignition are good

 

Just remembered also, a family member of mine also had a intermittent miss with a 2002ish F150 with a 4.6 ended up having to take it to a dealership finally to hook up to some piece of equipment they had, the computer at other places would show an miss but no code except the one bad pack which we did replace. But that didn't fix it, they ended up having to have it hooked up to something while driving it around before it finally showed them what was up. It ended up being all together 3 bad coil packs that the other readers only showed that one of was bad.