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daddytall

daddytall

Well-known member
Joined
May 19, 2020
Member Number
102
Messages
64
2004 WJ 4.7 Throws code 307 Cylinder misfire, Things I have tried

new coil packs
new spark plugs
rebuilt heads
switched fuel injectors
compression/leakdown test

No matter what I do, cylinder 7 has a misfire. I *think* the misfire goes away after idle as the thing runs great except for a loopy idle. Doesnt throw the check engine light, but the goverment wont give me my papers until I fix the problem.

Also. htf does the ecu know its cylinder 7 that is misfiring? :homer:
 
daddytall said:
2004 WJ 4.7 Throws code 307 Cylinder misfire, Things I have tried



Also. htf does the ecu know its cylinder 7 that is misfiring? :homer:
Click to expand...

not sure if serious question but it uses the knock sensor along with the crank sensor to determine which cylinder is having a missfire.

You have done way more than I would have, I have no further ideas of what you could try.
 
crispins said:
not sure if serious question but it uses the knock sensor along with the crank sensor to determine which cylinder is having a missfire.

You have done way more than I would have, I have no further ideas of what you could try.
Click to expand...

I bought the thing for $500 with a dropped valve seat (cyl 4) and threw all those parts at it getting it running. Now I would like for it to work all the way. And yes it was a serious question lol
 
crispins said:
not sure if serious question but it uses the knock sensor along with the crank sensor to determine which cylinder is having a missfire.
Click to expand...

no, idiot
ckp would only tell one of two cylinders and knock sensors don't have shit to do with it
it uses the cam sensor to tell which cylinder it is, and it tells when it misfires because the engine RPM slows down from the one missing power stroke on a misfire
 
new doesn't mean good, it stands for "never even worked"
switch the coil packs and plugs around on the dead hole

hose down the intake gaskets with brake cleaner to see if you've got a vacuum leak
 
[486 said:
;n205282]

no, idiot
ckp would only tell one of two cylinders and knock sensors don't have shit to do with it
it uses the cam sensor to tell which cylinder it is, and it tells when it misfires because the engine RPM slows down from the one missing power stroke on a misfire
Click to expand...

Damn dude you sound like a real ass, straight up butt hole. Calm down or clam up.
 
Noid test is basically plug in a 10-15w bulb instead of an injector and see if it blinks as it should when the injector should be spraying. Any more, you can add a meter into the mix to check duty cycle and frequency and compare to other injectors pretty easily.
 
daddytall said:
What the heck, might as well
Click to expand...

Don't bother, that isn't going to fix it.

Did you replace or rebuild the heads or just fix the one bad valve seat?

It could be several things.....

-Dying injector (swap to a different cylinder to check)
-Low compression in that cylinder (bad rings or burnt valve)
-Another valve seat falling out
-Slightly bent valve due to the above problem
 
ScottRS said:
Noid test is basically plug in a 10-15w bulb instead of an injector and see if it blinks as it should when the injector should be spraying. Any more, you can add a meter into the mix to check duty cycle and frequency and compare to other injectors pretty easily.
Click to expand...

There goes my Sunday
 
SLOWPOKE693 said:
Don't bother, that isn't going to fix it.

Did you replace or rebuild the heads or just fix the one bad valve seat?

It could be several things.....

-Dying injector (swap to a different cylinder to check)
-Low compression in that cylinder (bad rings or burnt valve)
-Another valve seat falling out
-Slightly bent valve due to the above problem
Click to expand...

Rebuilt heads from reputable shop
Checked all those other things
 
daddytall said:
Rebuilt heads from reputable shop
Checked all those other things
Click to expand...

If its only throwing a code for that one cylinder and no other codes for sensors ect there is a 95% chance its mechanical.

Results from leakdown test of all cylinders?
Compression test results?

Even reputable shops fuck up sometimes
 
Don't know if it'll help, but if the injector plugs are the same bosch plug as ford/gm, I have a noid light and a breakout pigtail to fit those. You're welcome to borrow either/both.
 
[486 said:
;n205296]
okay, fill up the forum with dipshits spouting bullshit as though they know what they're talking about
oh wait they've already got a forum like that, it's called reddit
Click to expand...

I chuckled but as you know I enjoy abuse.

You did come off a bit hasty but hey. You certainly know a lot about how that ECU works if you're right.
 
486 has the best advice so far.

If it only misses at idle there could just be a vacuum leak near cylinder 7 too. Someone suggested spraying the intake with brake cleaner to see if the motor changes speed to verify. Thats good advice but I recommend using carb cleaner instead.

And dont dick around with noid lights if it runs fine off idle, if it doesnt then play ball.
 
evernoob said:
You did come off a bit hasty but hey.
Click to expand...

jesus fuck apparently "idiot" is the end-all insult that the only response to is suicide

I used to hang out here because it wasn't a fuckin' 'safe space'
if we're coddling idiots that were stumped by a stripped drainplug spewing wrong answers to innocent impressionable minds now, I might just accept the fact that the pbb really did die
 
[486 said:
;n205282]

no, idiot
ckp would only tell one of two cylinders and knock sensors don't have shit to do with it
it uses the cam sensor to tell which cylinder it is, and it tells when it misfires because the engine RPM slows down from the one missing power stroke on a misfire
Click to expand...

Damn dude what crawled up your ass tonight, oh wait, never mind I don't want to know.

No reason to be such a fucking dick.
 
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[486 said:
;n205340]

jesus fuck apparently "idiot" is the end-all insult that the only response to is suicide

I used to hang out here because it wasn't a fuckin' 'safe space'
if we're coddling idiots that were stumped by a stripped drainplug spewing wrong answers to innocent impressionable minds now, I might just accept the fact that the pbb really did die
Click to expand...

I thought my 486 ass jokes were pretty obvious, guess not. No safe spaces here:flipoff2:
 
You said you replaced the heads... I fought a cyl 2 and 3 misfire on a 4.7L while going up grades for a long time. Checked compression, changed coils, plugs, O2 sensors, etc. The only thing that fixed it was replacing the heads after one of the #2 seats finally dropped. I've got a nice dremmeled divot in that cylinder to round out the damage from the seat, but it's put 30k trouble free, misfire free miles since.
 
[486 said:
;n205467]
nope, you just came off as butthurt
Click to expand...

A little prodding and you were crying, I thought you would have been use to it by now.
 
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