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Old 08-19-2010, 06:22 AM
UB267 UB267 is offline
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Misfire #3, PO 303 & 316

My 2002 F150 4.2L used to be my primary vehicle, but I just switched & started to park it in my barn. It gets used at least once a week, if not more. Engine was running well until about a week ago. Runs very rough under load and idle is rough. My tester shows codes 303 & 316. After searching the forums (great stuff here!) I have replace the coil pack, wires & plug on #3 with no results. Last night I cleaned the EGR ports, but no luck there. That leads me to believe it's an injector problem, but not certain. Once I get above 2,000 RPM it seems to smooth out. Am I on the right track here? Also, is it possible to remove the #3 injector without tearing off the air intake plenum?

Thanks in advance for any help!
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Old 08-21-2010, 11:34 AM
UB267 UB267 is offline
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Question Now really confused

I've been trying to narrow this down for a week now! Guess the truck is upset that it's not #1 anymore.

Reset the codes & drove it a short distance. CEL comes back on & the new codes are 316 & 302! Sure enough, no spark on #2 only. Then tried the following:

Changed plug wire twice=no spark
Changed plug three times=no spark
Tested resistance to terminal right next to #2 on coil pack (the one that fires with it) & shows OK (that terminal is firing strong)
Tested the old coil pack to verify that it was bad=it was

Does anybody have any ideas? I can't make any sense of this.

Thanks,
UB
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Old 08-23-2010, 02:13 PM
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BrianA BrianA is offline
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Yeah, confusing ?? alright.

Any chance you have 2 bad coil packs?
From what I read:
original coil pack = no fire on #3.
new coil pack = no fire on #2.
Could you put the original back in and see if the problem with #2 clears and problem with #3 returns?

Sounds like you know what you are doing as far as checking things. Keep us posted.
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Old 08-24-2010, 09:24 AM
UB267 UB267 is offline
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Problem Solved

Took off the new coil pack & took it back for a replacement. The new one works fine. Lots of time invested trying to figure this out when it was a faulty new part! Thanks for the suggestion Brian, you were right on.
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Old 08-24-2010, 08:13 PM
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BrianA BrianA is offline
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Hey, even a blind squirrel finds an acorn every now and then.

Glad you got it squared away!
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Old 08-24-2010, 08:13 PM
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2003, 303, 316, 38, 3o3, code, codigo, cop, engine, escape, f150, ford, misfire, po, po303

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