I need help
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New User
Joined: Oct 2006
Posts: 4
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I need help
'03 f150 5.4l.....DTC's P0303 and P0316. Rough idle, misfires when at freway speeds (65-75 mph). Know it's the 3rd cylinder. Replaced the coil pac, tested the ignition wire and the injector wire, changed spark plug,checked fuel pressure on rail, and compression test on #3. I'm clueless. Had head gasket replaced and the mechanic didn't hook up the vacume line to the fuel volume regulator or the cam sensor. Timing off??? Maybe reset the ECM???
Thread Starter
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New User
Joined: Oct 2006
Posts: 4
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Will check them all now. I've been hearing from other people that the DTC's are pretty ****ty. One guy had misfire on #1 and it turned out being #5. Only thing I hate about this truck is the OBD II system
Fleet Mechanic
Joined: May 2005
Posts: 1,739
Likes: 14
From: Vale, NC
There's some interesting stuff on here aboput these coil packs and how they will misfore without throwing a code. When I first got my truck it started missing under light accelaration and only between about 45 and 65. It got a bit worse but never threw a code. Kind of a bucking sensation. After reading on here a great post by Bluegrass7 where he explained how it happens under light load, I replace all the cops with the Accel ones off eBay and got myself a new set of plugs. It has run fine ever since.
Good luck
Good luck
