P0307

[saleen07gt]

I'm about a week away from putting on a set of ported cyl heads, frpp intake, gt500 tb and injectors and all of a sudden the car is intermittantly missfiring and setting a P0307 (misfire #7 cyl). No big deal, I've got new motocraft spark plugs, so I installed one new motocraft spark plug and coil in #7, cleared the code and the car seemed ok, until today. It is still setting a P0307, so I swapped #7 injector with #6, cleared the code, testdrove it and still intermittantly setting a P0307. WTF ?

 

[eighty6gt]

Wiring... or mechanical.

 

[saleen07gt]

Wiring... or mechanical.

I don't think it's mechanical, it would be missfiring all the time. I drove it tonight, it was missfiring, ck engine light flashing for a few miles then all of a sudden smoothed out and ran great for the next 20 miles. Could it be a false code, maybe one of the other cyls are actually missfiring ? I'm going to change the rest of the spark plugs in the morning.

 

[Sprayer84]

Swap the injector. Could also be throwing a code for the wrong cylinder. Need to do a power balance test with a scan tool


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[Kalatrax]

That leaves it with a wiring issue. Probably a loose pigtail or worn off insulation on the injector or coil wires.

 

[saleen07gt]

Update : I'm losing the injector pulse for the first 5-10 mins during startup then the pulse comes back andwill run fine for hours after that. It acts like the injector driver in the PCM is failing.

 

[Sprayer84]

That doesn't sound good. It's strange that it only is doing it on startup.


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[saleen07gt]

It is strange, it litteraly won't pulse #7 injector for the first 6 mins during a cold startup, by the 7th min, the injector is working and the engine is running smoothly.

 

[JeremyH]

Make sure the injector plug is tight and the wires going in are good. When its not working on startup I would go wiggle the connector and push it tight and see if you get pulse.

 

[saleen07gt]

Make sure the injector plug is tight and the wires going in are good. When its not working on startup I would go wiggle the connector and push it tight and see if you get pulse.

I did a wiggle test from the injector all the way to the PCM, nothing changed, I guess I could ohm out the wires from the PCM to the injector before I buy a PCM.

 

[saleen07gt]

Update : I suspected the PCM to be faulty (injector driver for #7 to be bad), priced out a new from Ford, almost $1,000 . Found a used one for $200, with the same part #and strategy code. It wouldn't start, had to program the PATS, that was $32.95, had access to a universal programmer. Uploaded my custom tune with the SCT and life is good again, car runs great, no more missfires. The place where I messed up was in programming the keys for the PATS, I was only able to get 1 key programmed, some how I made the wrong selection in programming tne 2nd key.