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?
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.
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.
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.