First off hi and thanks for any help that may be provided. Sorry my first post here has to be asking for help but im stuck and need some direction.

1998 4.5

Truck started bogging realy bad yesterday and the check engine light came on.
When i got home i threw the good ole scanner on it and pulled a powertrain code of 304. {missfire on cylinder 4} Now i have heard of an issue with the heater hose leaking on the cylinder 4 coil pack. So i figured it was time to change the plugs anyway so why not make a day of it.
When i pulled the plugs THEY WHERE HORRID. So much crap stuck solid around the electrode that i figured this HAD TO BE the issue. Replaced all 8 plugs and to be safe i put the #4 coil pack up front so if it was bad it would be easy to pull this time. Also fixed a vacum leak i found.

Started it back up and it seem to idle fine but with a little gas it was still boggin bad from 0-45 mph. After 45mph if you get on the gas it seams as if nothing is wrong has power just as it should be.
Took it for a ride around the block and the check engine light cam back on. This time giving me the code of 354
{ primary/ secondary circut on cylinder D}. D is cylinder 4 right?
Different code same cylinder with a different coil pack?




I also checked the ohm resistance to make sure the ground to that coil pack wasnt grounded out some where.

Im soooooo sorry this was so long but any info or leads would be greatly apreciated.

Thanks
R James.

 

Perhaps a different problem on cylinder 4? If the plug came out fouled, it is possible that the one you just dropped in is also fouled. However, a fouled plug should get worse with more throttle not better. So this confuses me.

None the less, based on the code the problem seems to be with the voltage going to the coil pack and not the plug itself. Can you get a good look at the wiring that leads to COP4?

 

Thanks for replying

I disconected the battery and distribution block and checked for voltage on both pins of the cop harness. I got a 9.2V ground connection on one and a 12v ground connection on the other.

I thought i shouldnt have any signal, why am i gettin a ground signal from both with the battery disconected?


Thanks R.James

 

Well got it all sorted out today. Couple wires got shorted out together and toasted the control units for the c.o.p's in the ecu. I was happy to find out that ecu's for this truck are cheap in compared to other vehicles.

Thanks