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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
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i'm getting the feeling that the jokes were missed on about 4 sides here :laughing:

suicide isn't a bad response to idiot for many people though :rasta:
 
daddytall said:
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:
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Can't pass an emissions test? or was the papers thing a joke? I'm trying to understand.:laughing:
 
If there is no CEL, I assume you are watching it on a decent scanner with a misfire counter? Does it show misfires above idle?

do a running compression check on the problem cylinder and a cylinder from the other bank to compare.

put a mechanics stethoscope on all the injectors at idle and at whatever rpm the miss seems to go away. Do they all sound the same?
 
daddytall said:
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:
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I have been thinking about this issue a lot since last night.

it is very unusual that you could still have a misfire in that same cylinder after everything you have done.

I would swap in a different Crank Sensor and see if the problem continues, if it does then fuck, register it somewhere else?
 
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[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
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I have read an article in the past that I thought suggested that the knock sensor combined with the crank sensor was used to determine misfires.

After researching the issue today I now know the knock sensor is not used for this purpose.

However, your suggestion that the crank sensor is not used is quite wrong.

This explains it pretty well.

https://www.underhoodservice.com/tech-feature-detecting-misfires-in-obd-ii-engines/


"The powertrain control module (PCM) notes the relative position of the crankshaft via the crankshaft position sensor (CKP) each time a trigger pulse is sent to the ignition system."
 
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[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
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To be fair he probably does actually have a stick up his ass. :laughing:
 
Curious to know if the plug looks any different than the others. or white, fouled, etc.

Next would be 486 advice, minus killing yourself with butt stuff.

Switch injectors, coils, wires, and shit around to see if anything changes.

You can "rent" a noid light kit from a parts house for $20. or buy one online for $20. Odds are they have a brand new kit still wrapped in plastic and you just rent it forever.
 
crispins said:
However, your suggestion that the crank sensor is not used is quite wrong.
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I never said that ckp wasn't used, just that it isn't used to determine which cylinder, what with having 2 crank revolutions per power stroke on any given cylinder, meaning you could only narrow it down to a cyl and its companion (unless you've got a disgusting 3 or 5 cyl)
 
Chased a similar problem on an F-350, it ended up being one of the new factory spark plugs I purchased had a loose electrode that shorted out on the tip. Obviously it was on the hardest cylinder to get to. Was kicking myself after picking through the wiring harness, checking every injector and coil pack connector with noid light, swapped coil packs around, started checking compression, etc.
 
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Gatorgrizz27 said:
Chased a similar problem on an F-350, it ended up being one of the new factory spark plugs I purchased had a loose electrode that shorted out on the tip. Obviously it was on the hardest cylinder to get to. Was kicking myself after picking through the wiring harness, checking every injector and coil pack connector with noid light, swapped coil packs around, started checking compression, etc.
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I had a plug once that I chased for a while. Turns out the electrode was loose so screwed in the cylinder it slid out and grounded itself. When I took it out I would hold it upside down so the electrode slid back in the plug and looked fine. I finally found the problem after swapping it to a couple different cylinders.
 
Well I went and played 27 holes of golf today instead of diagnosing the misfire :homer: I did order a new coil, injector and crank sensor. Will add a sparkplug to that order. I really like the car and would like it to be my new daily driver. Thanksgiving weekend is my plan to fix it or burn it to the ground. Will report back
 
shortbus4x4 said:
I had a plug once that I chased for a while. Turns out the electrode was loose so screwed in the cylinder it slid out and grounded itself. When I took it out I would hold it upside down so the electrode slid back in the plug and looked fine. I finally found the problem after swapping it to a couple different cylinders.
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Yep. I pulled it out with the electrode down and saw it touching the tip, thought “shit, that’s from a broken valve.” Turned it upside down for a better look and ll was fine. My point was a lot of times we consider new parts to be out of the diagnostic circuit but that’s not always the case.
 
daddytall said:
Well I went and played 27 holes of golf today instead of diagnosing the misfire :homer: I did order a new coil, injector and crank sensor. Will add a sparkplug to that order. I really like the car and would like it to be my new daily driver. Thanksgiving weekend is my plan to fix it or burn it to the ground. Will report back
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The other thing you can do is just walk away from it for a week. A lot of times extremely difficult problems seem to have very simple solutions once you start back at it with a fresh mind.
 
Gatorgrizz27 said:
The other thing you can do is just walk away from it for a week. A lot of times extremely difficult problems seem to have very simple solutions once you start back at it with a fresh mind.
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That and explaining your problem to someone who knows nothing about said problem, thus this thread. lol I am going to start over and try everything again. A noid light kit was $27 so I ordered one. New coil pack, spark plug, injector, ckp, You know, throw parts at it. :homer: That and compression check and leakdown test again, noid test, and whatever else I can think of. Its gotten to the point that I HAVE to figure it out
 
you still haven't said if you've hosed down the intake gasket regions with brake clean to see a vacuum leak

Suppose I could explain the reasoning further,
idle has high manifold vacuum, real low cylinder pressures, so that pretty well rules out ignition, it would get worse with increased manifold/cylinder pressure not better, as the increased cylinder pressure makes the air in the spark gap more dielectric, meaning higher spark voltages and more chance of spark leakage.
Also, dwell time on the coils can be higher at low RPM, so you can get a stronger spark (unless the ECU is capping it at whatever millisecond value it would be at max RPM). More a distributor thing than coil on plug, but still.

also, again, idle has high manifold vacuum, meaning it is going to suck in more air from that pinched gasket, and with the very low mass air flow of idle it will affect the mixture in that one runner much more significantly than with higher mass flow above idle where it is leaking a little less from the lower vacuum and atop that there is more of an intake charge to dilute the false air that the ecu doesn't "know about" that is going in that one cylinder

ETA: also, the injector might be flowing less than the others, but you say you switched them around so that rules it out pretty definitively. More load means more pulsewidth through the injector, so it clearing up with increased load points away from resistance in the harness, too.
 
Welp, yanked the intake and replaced all the gaskets, threw in a new coil and injector, verified spark and noid light on injectors. Spark plug looked fine, Still a miss in cyl 7 FML
 
this is why you do diag before throwing parts at it
you hose the shit down yet?
I don't remember if those have a plastic intake or not, you can run into split seams
 
[486 said:
;n223556]this is why you do diag before throwing parts at it
you hose the shit down yet?
I don't remember if those have a plastic intake or not, you can run into split seams
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Hosed it. Inspected the plastic, "looked" fine. I hear you on throwing parts at it being dumb, but I'm a carpenter :homer:
 
daddytall said:
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
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My father in law did the exact same thing, except he fully rebuilt the entire motor. He's a "while I'm there" guy, so he spent a dick load on new rad, new hoses, new brakes, cv axles, ect. He gets it going and it was kinda a money pit. Heater core, brakes again, sensors, ect.

It ended up burning in a wild fire, I asked him about getting another one cause I thought he really liked it. He said he hated it. He got car sick twice while driving it :lmao:

Sell it now!
 
daddytall said:
Hosed it. Inspected the plastic, "looked" fine. I hear you on throwing parts at it being dumb, but I'm a carpenter :homer:
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is your brake cleaner the flammable kind?
made the mistake of buying the non-flammable kind once, never again:laughing:
 
how about big vacuum lines that are hooked up to the intake, like the brake booster and PCV
if they are soft rubber try pinching them off, if they're hard or plastic don't you dare touch them they'll break into a billion pieces, just spray some on their whole length
brake boosters can fail into vacuum leaks too
 
pull the valve cover and make sure the rockers are all where they should be, i`ve seen quite a few 4.7 engine that spit a rocker out and has a misfire code and feels like it`s fine when your accelerating.
 
daddytall said:
Welp, yanked the intake and replaced all the gaskets, threw in a new coil and injector, verified spark and noid light on injectors. Spark plug looked fine, Still a miss in cyl 7 FML
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did you check and confirm the dumb little spring is neither missing or broken inside the coil-on-plug boot?
 
Also, ECMs is not always is right on which cylinder is misfiring. Check all cylinders!

or your ECM is bad :lmao:

My ‘98 XJ’s ECM went bad, followed with a nasty lope idle. ECM failed internally via permanently grounding cylinder 3 injector circuit. :eek:
 
This thread sure would be better in a tech thread. That way I wouldn’t have to read through all the ghey ass stupid posts while reading about a bit of info..
 
Brian468 said:
pull the valve cover and make sure the rockers are all where they should be, i`ve seen quite a few 4.7 engine that spit a rocker out and has a misfire code and feels like it`s fine when your accelerating.
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Haven't been inside a 4.7, but we did just pull a 5.7 with a bad misfire and tick on 7. Tossed a junkyard motor in it. Once out pulled the valve cover and found the little block that holds the rocker shaft to the head had broken. 2 of them. That allowed the rocker to move off the stem. Doh.
 
I think it hates me. I put new lifters and rockers as part of my "That should do it!" parts throwing brigade. I love the thing except for this issue.
 
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