I have a 1997 F150 4x4 with 5.4l an 124,000 miles on it.The spark plugs were changed around 118k to 120k. A week or so after this the truck got a misfire. I took it back in the mechanic replaced one COP and he also said he replaced the connector. It never had a check engine light on. The truck is now misfiring again a year later and no check engine light. My question is will a code still be thrown even if no light on dash comes on. Also how do you test the COPs.

 

Yes, there very well could be a code stored, even w/o a check engine light. One simple way to test the coils is to swap them. Have codes pulled, and swap the coil from the cylinder that is misfiring to one that isn't, and see if the fault code moves to that cylinder. In other words, if you retrieve a P0304 (cylinder 4 misfire,) move cylinder number 4's coil to any other cylinder, say cylinder number 1. Clear codes, and than pull them again. If you now have a code for cylinder number 1 misfire (P0301,) you have a bad coil. Not an exact science, but it will work. You just don't want to drive very far with a misfire, bad things happen. Very bad things. A good shop will have more advanced equipment to test the coils, so it's kind of personal choice thing: take it to a shop that can diagnose the coils, but have to pay, or try to do it yourself with no equipment, but save the cash...

 

Depends on how the miss shows up.
If betweeen 45 and 60 under light throttle it's a cop and won't set a code because it is not a hard fault.
Problem is which cylinder is it?
Good luck.

 

Its more like an all the time thing the truck does not idle smooth either and bucks when you accelerate.

 

I got the truck back from mechanic today and he wrote down that the truck had two history codes PO 302 and PO 305 and that it would need two ignition coils to fix these. Also where is the check engine light at on these trucks or where is supposed to be. I have never had a light come on and no light comes on when the key is turned on but truck is not running which on other cars I have owned the light is on. What I am thinking is the bulb is burned out. How hard is to get the instrument cluster to change the bulbs in the back and does anyone know how many bulbs it is.