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Old 10-14-2011, 02:13 AM   #1
hendo832

 
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Default misfire on #3 cyl. please help!!

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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Old 10-14-2011, 11:03 AM   #2
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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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Old 10-14-2011, 09:52 PM   #3
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yea that and a leak down test are my next steps. im just curious if anyone knew a little secret from experience ya know...thanks man
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Old 10-14-2011, 09:59 PM   #4
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When you checked the compression on #3 did you pull all the other plugs and block the throttle open? If not you have an invalid test, pull 'em all, block the TB open, and test 'em all.

Doing this will provide a solid baseline. The lowest should be at least 75% of the highest...
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Old 10-20-2011, 10:41 PM   #5
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NO I DIDNT!!! I DIDNT KNOW I HAD TOO...OOPS!!! LOL. OK SO I WILL GET THAT DONE IN THE NEXT DAY OR TWO...THANKS FOR THE HELP CLIFF I APPRECIATE THE ADVICE MAN
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Old 10-20-2011, 11:43 PM   #6
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FWIW; Per common internet protocol, ALL CAPS IS YELLING--however beyond that it is more difficult for humans to read.

By making it more difficult to read, fewer people will bother to read your messages and you will have fewer responses...
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Old 10-21-2011, 12:39 PM   #7
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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.
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Old 04-16-2014, 12:32 PM   #8
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I have the same problem with my 97 gt. I 2 squirts of oil down cylinder 4 but my compression shot up from 129 to 170. Done rings?
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Old 04-17-2014, 09:10 AM   #9
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Quote:
Originally Posted by manuels14 View Post
I have the same problem with my 97 gt. I 2 squirts of oil down cylinder 4 but my compression shot up from 129 to 170. Done rings?
Yup...
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Old 04-17-2014, 01:49 PM   #10
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Quote:
Originally Posted by cliffyk View Post
Yup...
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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Old 04-17-2014, 01:49 PM
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