4.6L (1996-2004 Modular) MustangTechnical discussions on 1996-2004 4.6 Liter Modular Motors (2V and 4V) within. Sponsored by Cruizin Concepts
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hey guys, i have an 02 gt with 82k miles, completly stock 4.6 & i have misfire on #3 and lacking power big time, its driving me crazy not being able to drive my car the way its supposed to be driven!!!!!! after this happened i replaced the plug, COP and swapped the injector to #1 and the misfire stayed on #3. the cop is getting voltage and i checked the injector wire with a noid tester and thats fine aswell...compression came back with 105 psi. i didnt check the other cylinders for comparison but i thought that was kinda low. anyone know off top what compression should be? also if i let the car idle for 10 minutes it starts to puff blue smoke (oil), and when i rev it up, the smoke comes even more...so this is signs of low compression right? so now i need to determine if its a piston ring or valves. i put 2 squirts of oil in the cylinder and rechecked compression and it came back the same 105psi... the codes its throwing are p0303 misfire on #3 and p0316 misfire in first 1000 revs. has anyone had this problem or suggest anything else before i pull the heads.....im not master certified or anything but i have a good idea what im doing and ive built a couple engines before. but this is my first mustang and not to familiar with the 4.6 but i heard a lot of good things about it. thanks guys i really appreciate any advice
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If the oil didn't bring the compression up, you could have a problem in the valvetrain. Before pulling the head, I would take the valve cover off and take a look. Rotate the engine over by hand and watch the valvetrain on cylinder 3.
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I had the exact problem on my 02 with 94k miles and did the same tests as far as swapping cops , plugs, and injectors..always #3 misfire after clearing codes every time....mine would up being a broken valve spring on #3 after pulling the valve cover ..easy fix.
Ok so then I should have lower compression right? I was told with the compression results that I got, that they were normal and within 15 percent of each other. On another note I checked fuel pressure it ran 32 psi at idle, then I half throttled and peaked up to 39psi but didn't hold. It lowered to 32psi at half throttle. Does this seem normal?
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