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2004 Ford Focus 2.0 had misfire codes Po302 P0303.
Initial troubleshooting led me to replace the waste spark coil. Starter was replaced prior to problem with coil. Coil had got hot and 2 plugs on the coil would not spark. Bottom of the coil was cracked. returned to customer after repair, car ran fine. Next day car left customer stranded on the road. Checked the car out second time. Same problem coil over heated and burned up. Replaced coil a second time ran for 2 or 3 minutes coil started to smoke and the second coil burned up. looking at wiring diagram shows a capacitor for radio noise suppression. Has any one found a bad capacitor to cause this problem? Reviewing Scanner Dan video on waste spark coils show transistors NPN controls the firing, could this be a possibility? Any suggestions would be appreciated.
Is there anything spliced into the ignition coil harness?
Most of the repeat failure ignition coils I see are from (poor) remote start installations. The tach wire usually gets spliced into a control wire on the coil, and it gets shorted to ground somewhere along the line and kills the coil.
As with Noah something shorting the control wire for that pair of cylinders to ground. On the Ford 4 cylinder coil pack the centre pin is +12v supply facing the socket on the coil the socket slot on the left is control for cylinders 1 & 4 cylinders the the pin on the right controls cylinders 2 & 3.
ISTR Coil winding for cylinders 1&4 are controlled by pin 10 on the edis module . the coil winding for 2&3 is controlled by pin 12 on the e-dis module . I would try unplugging the coil and the e-dis and measuring the resistance between the ground and pins 10 & 12 on the edis and also the outer pins on the coil pack and ground. If this okay then you have to look at the Edis unit, the wiring between the Edis and PCM or the PCM.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
Cheryl I would say to get that much over heat damage it has to be on the primary circuit of the coil. Old guys like me used to see that kind of coil burn out issue on old style contact breaker ignitions where a ballast resistor was missing or where the owner had left the ignition on for extended periods with the engine off. With a scope and an amp clamp it would be easier to track down, re-reading Auto58's original post and Noah's answer I think Noah may have hit the nail on the head the problem could something in the wiring that was disturbed when the starter was changed.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
Thanks for the information. It has put me on the right track. If the problem is with the PCM would the pin that provides the ground to control wire for cylinders 2&3 be grounded? Again thanks for your input.
Mike
I think a voltage measurement aft the coil would be a good place to start.
With the key on, engine off and the coil plugged in, all the wires on the coil connector should read battery voltage.
If the the control wire for the pair of missing cylinders shows ground, then the problem is a short in the harness, or the PCM driver is shorted internal.
So if you do find that the control wire is always grounded, you can disconnect the PCM and recheck. If the control wire was grounded with the PCM connected and then not with the PCM disconnected, then it's most likely the PCM is at fault.
I've seen it before in other Ford products.
Of course, if you find the control wire remains grounded with the PCM disconnected, then there's a problem with the harness shorting to ground.
if the new coils last a day or 2 then burning up you could always try swapping the control wires at the pcm. should be 2 of them that control 2 cylinders a piece. and if coils 1 and 3 burn out your done put a pcm in it. BUT if there burning up instantly do check the control wires for a short to ground
do you think I could install a in line fuse just for testing purpose? this would keep the harness and coil from, burning up until I find the problem. I think a 20 amp fuse should do the trick . this would only be temp till I find the problem.
thanks for your input.
mike
