97 4.6 P0308 code - Ford F150 Forum

sproosemoose · 11-09-2009, 10:44 AM

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?

sproosemoose · 11-10-2009, 10:24 PM

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?

jeremy 08 · 11-13-2009, 06:04 PM

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

Kattumaram · 11-13-2009, 08:49 PM

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.

sproosemoose · 11-14-2009, 09:26 AM

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.