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post #1 of 13 Old 06-15-2019, 09:06 PM Thread Starter
Randomlyawesom
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Multiple misfires

Just got a new engine in. I have a multiple misfire code, and codes for misfires on 5 4 and 2. 5 comes quick and 4 and 2 come after awhile of driving. All the connections seem good. The misfires on 2 and 4 only happen when driving and 5 slowly happens at random even at idle. I remove the coil connector for 5 and it gets tougher so it can’t be a dead cylinder. Next plan is to swap coil packs and see if it follows. If not I’ll check the plugs. Anyone had a problem similar to this?

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post #2 of 13 Old 06-16-2019, 09:50 AM
Mattyjm
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Originally Posted by Randomlyawesom View Post
Just got a new engine in. I have a multiple misfire code, and codes for misfires on 5 4 and 2. 5 comes quick and 4 and 2 come after awhile of driving. All the connections seem good. The misfires on 2 and 4 only happen when driving and 5 slowly happens at random even at idle. I remove the coil connector for 5 and it gets tougher so it canít be a dead cylinder. Next plan is to swap coil packs and see if it follows. If not Iíll check the plugs. Anyone had a problem similar to this?
Well, we're all assuming you're asking about a 4.7L V8, since we don't know for sure as to what engine you have in your WJ. But you must have the V8, otherwise, you wouldn't have single coil packs to deal with.

What spark plugs are you running in it? What year is your WJ? How many miles are on the new engine? Was it a junkyard swap or did you purchase a new long block?

2002 Laredo. Baloo.
2004 Rocky Mountain Edition. Froggy Bandit. Wife's Daily Driver. PRISTINE! Stock height and may stay that way.....
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post #3 of 13 Old 06-17-2019, 05:09 PM Thread Starter
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Quote:
Originally Posted by Randomlyawesom View Post
Just got a new engine in. I have a multiple misfire code, and codes for misfires on 5 4 and 2. 5 comes quick and 4 and 2 come after awhile of driving. All the connections seem good. The misfires on 2 and 4 only happen when driving and 5 slowly happens at random even at idle. I remove the coil connector for 5 and it gets tougher so it can’t be a dead cylinder. Next plan is to swap coil packs and see if it follows. If not I’ll check the plugs. Anyone had a problem similar to this?
Well, we're all assuming you're asking about a 4.7L V8, since we don't know for sure as to what engine you have in your WJ. But you must have the V8, otherwise, you wouldn't have single coil packs to deal with.

What spark plugs are you running in it? What year is your WJ? How many miles are on the new engine? Was it a junkyard swap or did you purchase a new long block?
90k premium used engine
4.7 v8
01 wj
Fixed misfire one 4, ended up being plug

5 and 2 still no prevail. No air leaks, good fuel, good comp. next is to test the wiring. If I unplug the coil while it’s running on 5 or 2, nothing changes
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post #4 of 13 Old 06-17-2019, 08:53 PM
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Check plugs. I believe they are 0.40" gap Champion single-platinums.
Change CoP packs to see if misfire changes cylinders.
Next would be injectors.

2004 WJ, 4.7HO, 2 cats, magnaflow
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post #5 of 13 Old 06-17-2019, 09:03 PM
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Originally Posted by Randomlyawesom View Post
90k premium used engine
4.7 v8
01 wj
Fixed misfire one 4, ended up being plug

5 and 2 still no prevail. No air leaks, good fuel, good comp. next is to test the wiring. If I unplug the coil while itís running on 5 or 2, nothing changes
Then I would guess the coils on 5 and 2 are bad and causing the misfires. If you unplug them and nothing changes, it's because they're NOT working.

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Originally Posted by MrBaz View Post
Check plugs. I believe they are 0.40" gap Champion single-platinums.
Change CoP packs to see if misfire changes cylinders.
Next would be injectors.
I don't know the gap for a 4.7L V8 plug, I do know that any plug with Platinum in the description is a BAD idea. You need Champion or NGK copper core spark plugs, even in a 4.7L V8. There's an FSM by Daimler-Chrysler somewhere that STRONGLY urges against using any spark plugs other than copper core.

2002 Laredo. Baloo.
2004 Rocky Mountain Edition. Froggy Bandit. Wife's Daily Driver. PRISTINE! Stock height and may stay that way.....
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post #6 of 13 Old 06-17-2019, 09:06 PM
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Originally Posted by Randomlyawesom View Post

Fixed misfire one 4, ended up being plug
This should be a STRONG indicator.

2002 Laredo. Baloo.
2004 Rocky Mountain Edition. Froggy Bandit. Wife's Daily Driver. PRISTINE! Stock height and may stay that way.....
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post #7 of 13 Old 06-18-2019, 10:56 AM Thread Starter
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Changed 5’s coil and plug. Plug was wet with fuel when I pulled it. Nothing changed. Changed 2’s coil and plug, nothing changed. Now I’m getting an open circuit code for 2’s injector so I have to dig into that. Why would 5 misfire with a new coil and plug and the old plug was wet with fuel
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post #8 of 13 Old 06-18-2019, 05:40 PM
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Quote:
Originally Posted by Mattyjm View Post
Then I would guess the coils on 5 and 2 are bad and causing the misfires. If you unplug them and nothing changes, it's because they're NOT working.



I don't know the gap for a 4.7L V8 plug, I do know that any plug with Platinum in the description is a BAD idea. You need Champion or NGK copper core spark plugs, even in a 4.7L V8. There's an FSM by Daimler-Chrysler somewhere that STRONGLY urges against using any spark plugs other than copper core.
My apologies. I was thinking of my jeep. The 4.7HO REQUIRES a single-platinum (per FSM). It is 0.040" gap.

Quote:
Originally Posted by Randomlyawesom View Post
Changed 5’s coil and plug. Plug was wet with fuel when I pulled it. Nothing changed. Changed 2’s coil and plug, nothing changed. Now I’m getting an open circuit code for 2’s injector so I have to dig into that. Why would 5 misfire with a new coil and plug and the old plug was wet with fuel
Wet plug? Too much fuel. Would match my assumption of running rich causing a misfire. Leaky injector. Time to replace.

2004 WJ, 4.7HO, 2 cats, magnaflow
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post #9 of 13 Old 06-18-2019, 08:14 PM Thread Starter
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Originally Posted by MrBaz View Post

Wet plug? Too much fuel. Would match my assumption of running rich causing a misfire. Leaky injector. Time to replace.
How hard is it to do injectors on these. I’m used to carburetors
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post #10 of 13 Old 06-18-2019, 08:32 PM
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Originally Posted by Randomlyawesom View Post
How hard is it to do injectors on these. Iím used to carburetors
The injector part is quite easy. It is getting to them that is the hard part.

You have to remove the coil packs, because they are in the way.
You've got to unplug nearly every single connection on top of the motor since the wiring loom is in the way.
You then need to make sure you have a fuel quick-disconnect tool to pop the feed line off the fuel rail.

Then you just remove 4 bolts (2 per side) and gently tug the rail until it releases. Pop the retaining clips off each injector and wiggle the old injector out. Easy, right?

And of course:
Quote:
Installation is the reverse of removal.

2004 WJ, 4.7HO, 2 cats, magnaflow
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post #11 of 13 Old 06-18-2019, 08:41 PM Thread Starter
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Quote:
Originally Posted by MrBaz View Post

The injector part is quite easy. It is getting to them that is the hard part.

You have to remove the coil packs, because they are in the way.
You've got to unplug nearly every single connection on top of the motor since the wiring loom is in the way.
You then need to make sure you have a fuel quick-disconnect tool to pop the feed line off the fuel rail.

Then you just remove 4 bolts (2 per side) and gently tug the rail until it releases. Pop the retaining clips off each injector and wiggle the old injector out. Easy, right?

And of course:
Quote:
Installation is the reverse of removal.
Alright I’ll see what happens
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post #12 of 13 Old 06-19-2019, 02:44 PM
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Originally Posted by Randomlyawesom View Post
Changed 5ís coil and plug. Plug was wet with fuel when I pulled it. Nothing changed. Changed 2ís coil and plug, nothing changed. Now Iím getting an open circuit code for 2ís injector so I have to dig into that. Why would 5 misfire with a new coil and plug and the old plug was wet with fuel
What codes are you getting? Here's a little something.

Found this. It's a TSB on the 4.7L V8.

Multiple injector circuit codes. MIL on, no noticeable driveability problems. May have code P0121 - TPS voltage does not agree with MAP. Possible codes P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208
System:
Emissions/PCM/Fuel
Codes:
P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208
Problem:
The PCM software falsely sets injector circuit codes when there is really no problem with the injectors. The problem is voltage spikes from the Throttle Position Sensor.
Test & Fix:
Throttle Position Sensor (TPS) voltage spikes greater than 0.02 volts trigger these false codes. Theoretically, this could be caused by an intermittent ground or other wiring connection. However in actual practice it is almost always a problem with the TPS itself. Due to the nature of this problem there is no conclusive way to test the TPS or the TPS circuit. If there are multiple injector circuit codes with no misfire, replace the TPS and clear the codes. something to look into:

2002 Laredo. Baloo.
2004 Rocky Mountain Edition. Froggy Bandit. Wife's Daily Driver. PRISTINE! Stock height and may stay that way.....
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post #13 of 13 Old 06-19-2019, 06:47 PM Thread Starter
Randomlyawesom
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Quote:
Originally Posted by Mattyjm View Post

What codes are you getting? Here's a little something.

Found this. It's a TSB on the 4.7L V8.

Multiple injector circuit codes. MIL on, no noticeable driveability problems. May have code P0121 - TPS voltage does not agree with MAP. Possible codes P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208
System:
Emissions/PCM/Fuel
Codes:
P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208
Problem:
The PCM software falsely sets injector circuit codes when there is really no problem with the injectors. The problem is voltage spikes from the Throttle Position Sensor.
Test & Fix:
Throttle Position Sensor (TPS) voltage spikes greater than 0.02 volts trigger these false codes. Theoretically, this could be caused by an intermittent ground or other wiring connection. However in actual practice it is almost always a problem with the TPS itself. Due to the nature of this problem there is no conclusive way to test the TPS or the TPS circuit. If there are multiple injector circuit codes with no misfire, replace the TPS and clear the codes. something to look into:
But... I am getting lots of misfires... I’m not sure how this could have anything to do with the misfires
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