97 4.6 P0308 code
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Junior Member
Joined: Mar 2008
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From: Ames, IA
97 4.6 P0308 code
Hey all. I've been trying to chase down a cylinder 8 misfire (p0308) in my 97 f150 with little success. I started by changing the plug. Then measured my plug wire, it was within spec (I'm using a chilton's for all my specs), replaced it anyway with no success. New coil pack. New fuel filter. Fuel pressure before and after the filter change was 30-31lbs. Goes to 45 with the vacuum line removed from the pressure regulator. Number 8 injector ohms within spec and after hooking up a noid light to the harness it appears to be functioning normally. I've got a whole can of seafoam in the tank with about 8 gallons of 87 octane to see if the injector cleans up. Compression check is next. Is there anything else I'm missing?
Thread Starter
Junior Member
Joined: Mar 2008
Posts: 21
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From: Ames, IA
pulled and replaced the #8 injector tonight. The old one had some junk on the end so i replaced it, took it for a test drive, and my misfire code came back. I've got a friend pulling some all-data stuff on it at his work tomorrow. anything else I'm missing?
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Joined: Nov 2009
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From: joliet
I had the same problem with my 97 V8 trition about 4 months ago a friend and i replaced the plugs and wires and disconnected the pos battery wire for 30 sec ever since then its been fine dont know if this will help at all
Retired Aerospace
Joined: Dec 2008
Posts: 1,324
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From: Edgewater, Florida
Strange Story:
Perhaps this is a silly question: Is the thing really misfiring or just throwing a CEL? The P0308 code thrown by my 97 4.6L a while ago turned out to be a bad plug wire that was causing an intermitent rough misfire at #8. I was chasing the injector as the culprit since a wiggle of the connector seemed to clear the miss......don't forget that #2 is fired in series with #8 and the misfire detection system is sometimes not too accurate (I'm not too sure how the thing knows which plug is misfiring) and might report a 308 rather than a 302.
Last edited by Kattumaram; Nov 13, 2009 at 08:53 PM.
Thread Starter
Junior Member
Joined: Mar 2008
Posts: 21
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From: Ames, IA
It's actually misfiring. Not at idle, not cruising along, but primarily when going uphill in "D". If the tranny downshifts the problem doesn't occur, but once you get a good load on it it starts to vibrate a lot and the light starts flashing. Slow down or stop and it idles just like there's nothing wrong.