98 Expy has a new motor, number one plug is miss fireing once in awhile..
it has new plug and wires. Is it the coil pack that is going or the injetor that is going. Thanks for the help...

 

Check to make sure your wire is connected good. I had a similar trouble with mine, the wire wouldn't stay on the plug.

Good Luck!

 

This is the third set of wires put onthe truck in the last two weeks. the shop i had put the motor in can't seem to fix it, i'm thinking its something else like the coil pack or injector. the truck dose NOT run rough it runs smooth even when the code comes up.

 

In that case, I would say see if flashing the PCM helps. If the motor is running fine, then it isn't missing. Just the computer is telling you it is. Also, if it is running fine, the injectors are working like they should.

The coils can be tested to see if they are working properly. Did the shop do that?