Coil 6 Insufficient Ionization, Multiple Cylinder Misfire, Fuel Injector 4 Circut/Open

2005 3.7L Liberty w/ ~180,000 Miles

Here are the codes:
[Key: RED = Current, GREEN = Resolved By Diag]
P0300 - Multiple Cylinder Misfire, this may come back due to the lower two codes, but the instant flash of it is gone I suspect due to the fouled looking spark plugs being changed...
P0204 - Fuel Injector 4 Circuit/Open
P2317 - Ignition Coil 6 Secondary Circuit - Low Ionization

Here are the symptoms:
Rough Idle
Will not rev past 2100/2200 RPM
Past 2200 RPM, the car needle "dances" up and down
Upon listening to injectors, some are clicking rapidly, some are slow and clacky. It's really hard to tell, but I'm assuming it may not be the injector itself given I've cleaned them and ran cleaner. I may replace these if suggested...

Here are my thoughts:
Initially, based on this post: https://www.jeepkj.com/threads/misfire-from-injector-wiring-circuit.69585/ I thought it may have been a wiring issue.
I therefor checked a lot of wires, and don't see any issues.
I may check voltage here soon, unsure on if that's at all helpful.
I feel like a shorted wire would be more obvious, and cause a lot more than two cylinders to basically go down the drain.

Here are steps I have taken to diag/fix this:
Battery Terminal Disconnect for 24 hrs to "relearn" (Done Twice, no help.)
Checked Fuses (All related fuses move power and don't appear burnt)
Swapped Coils 6 and 1 to rule out the coil 6 (Problem persists in cylinder 6)
Cleaned all 6 injectors (Beginning to suspect I should order new injectors...)
Cleaned entire fuel system and switched to Shell 93 for a full tank of driving (No help, just as the injector cleaning)
Inspected wires to/from coil 6, injector 4, and PCM (No damage apparent? Moving the wires did nothing as well, which I believe would not be the case if it was shorting out.)
Swapped Relay for ASD with Lower Rad Fan (No change, rules out ASD Relay Failure)
Pulled, Inspected, and cleaned up all PCM plugs (Ideally hoping the PCM itself isn't going bad, although as many have mentioned on here, that would come with more signs than just a coil 6 low ionization.)
New Fuel Filter
Cleaned Throttle Body

Possible Solutions:
Compression Test #2 will be completed in the next day or two
Will likely buy a new set of injectors if it passes.

Hoping someone like @Billwill could help?

You can move the coolant tank out of the way without disconnecting the hoses. The manual advises against premium gasoline. Regular or Mid Grade depending on conditions.

Compression test would be worth doing.

KJowner said:

Compression test would be worth doing.

Click to expand...

It passed compression, everything was above 170 and below 220.

klc said:

You can move the coolant tank out of the way without disconnecting the hoses. The manual advises against premium gasoline. Regular or Mid Grade depending on conditions.

Click to expand...

This was only for the detergents. And while I am aware of this, it is still going to need to be at a bad angle.
I decided to go with the route of using a sewing needle to sort of "vampire bite" into the wires I wanted to test. Saw a video on it today, so I'll be checking all of the wires for coils 4 and 6, and injectors 4 and 6 as well sometime either tonight or tomorrow depending on free time...


So far, after owning a 2004 2wd Liberty, and 2006 4wd Liberty, and now this 2005 4wd Liberty the only thing I have concluded is Mopar being Mopar.

FCSSensai said:

2005 3.7L Liberty w/ ~180,000 Miles

Here are the codes:
P0300 - Multiple Cylinder Misfire
P0204 - Fuel Injector 4 Circuit/Open
P2317 - Ignition Coil 6 Secondary Circuit - Low Ionization
P0300 - Multiple Cylinder Misfire

Hard Misfire w/ blinking engine light at idle, anything past ~2100 RPM will make it shutter / jerk back and forward with the RPM going up and down. Car cannot pass 55 MPH and takes FOREVER to get there. At low speed, simply getting the thing moving especially in reverse is rather hard.

Thinking based on this post: https://www.jeepkj.com/threads/misfire-from-injector-wiring-circuit.69585/ it might be a wiring issue.

Here's what I have done to try to diag this:
Battery Terminal Disconnect for 24 hrs to "relearn"
Checked Fuses = All have power properly
Swapped Coil 6 and Coil 1, problem stayed in cyl 6.
Swapped Coil 6 for a brand new coil, problem got worse in the same cyl.
Cleaned all 6 injectors. No help.
Cleaned entire fuel system and switched to Shell 93. No help.
Inspected wires to cyl 6, cyl 4, Injector 4, and Injector 6. No visual damage. (Wondering how I'd check power w/o car running... as to get to cyl 6 I need to take the air tube and coolant res off.

Hoping someone like @Billwill could help?

Click to expand...

Have you got any smoke at all coming out of the tailpipe? If "yes", STOP DRIVING IMMEDIATELY. That was the precursor to a blown ring. Smoke messes up the catalytic converters (min $1500 for a complete new exhaust system because that junk cakes up in the pipes and finds its way downstream).

If "no", there are actually 3 PCV valves on a 6 cyl. One off the right front (your left if you are facing the engine compartment) corner, and 2 more (one on each side of the air intake on top of the manifold) inline in the intake breather tubes.

If you replace the block side PCV, be VERY careful about the twist-and-pull to pop it out. Look on youtube for guidance. If you snap the plastic tab you will not be able to put a new one in until you dig the broken bits out of the socket.
There are also

dtennes said:

Have you got any smoke at all coming out of the tailpipe? If "yes", STOP DRIVING IMMEDIATELY. That was the precursor to a blown ring. Smoke messes up the catalytic converters (min $1500 for a complete new exhaust system because that junk cakes up in the pipes and finds its way downstream).

If "no", there are actually 3 PCV valves on a 6 cyl. One off the right front (your left if you are facing the engine compartment) corner, and 2 more (one on each side of the air intake on top of the manifold) inline in the intake breather tubes.

If you replace the block side PCV, be VERY careful about the twist-and-pull to pop it out. Look on youtube for guidance. If you snap the plastic tab you will not be able to put a new one in until you dig the broken bits out of the socket.
There are also

Click to expand...

No smoke.
I do have a small EVAP code that showed once.
Any reason(s) why you're suspecting the PCV Valve(s) from this?

FCSSensai said:

2005 3.7L Liberty w/ ~180,000 Miles

Here are the codes:
P0300 - Multiple Cylinder Misfire
P0204 - Fuel Injector 4 Circuit/Open
P2317 - Ignition Coil 6 Secondary Circuit - Low Ionization
P0300 - Multiple Cylinder Misfire

Hard Misfire w/ blinking engine light at idle, anything past ~2100 RPM will make it shutter / jerk back and forward with the RPM going up and down. Car cannot pass 55 MPH and takes FOREVER to get there. At low speed, simply getting the thing moving especially in reverse is rather hard.

Thinking based on this post: https://www.jeepkj.com/threads/misfire-from-injector-wiring-circuit.69585/ it might be a wiring issue.

Here's what I have done to try to diag this:
Battery Terminal Disconnect for 24 hrs to "relearn"
Checked Fuses = All have power properly
Swapped Coil 6 and Coil 1, problem stayed in cyl 6.
Swapped Coil 6 for a brand new coil, problem got worse in the same cyl.
Cleaned all 6 injectors. No help.
Cleaned entire fuel system and switched to Shell 93. No help.
Inspected wires to cyl 6, cyl 4, Injector 4, and Injector 6. No visual damage. (Wondering how I'd check power w/o car running... as to get to cyl 6 I need to take the air tube and coolant res off.

Hoping someone like @Billwill could help?

Click to expand...

I don't see replaced spark plugs? Also remove throttle body and clean (remove all black carbon) last put 2 big bottles of Chevron Techron complete engine cleaner.

Xterra4x4 said:

I don't see replaced spark plugs? Also remove throttle body and clean (remove all black carbon) last put 2 big bottles of Chevron Techron complete engine cleaner.

Click to expand...

Cleaner has been run, I'll go get some sparkplugs this week.

Xterra4x4 said:

I don't see replaced spark plugs? Also remove throttle body and clean (remove all black carbon) last put 2 big bottles of Chevron Techron complete engine cleaner.

Click to expand...

2nd Tank of Cleaner, no luck.
New Sparks, no luck.... although it seemed to run a *little* smoother, and the misfire codes went away.
Only remaining codes are:
P0204 - Fuel Injector 4 Circuit/Open
P2317 - Ignition Coil 6 Secondary Circuit - Low Ionization
Still suffering from basically falling flat on it's face past 2100 RPM, and idling poorly.

FCSSensai said:

2005 3.7L Liberty w/ ~180,000 Miles

Here are the codes:
[Key: RED = Current, GREEN = Resolved By Diag]
P0300 - Multiple Cylinder Misfire, this may come back due to the lower two codes, but the instant flash of it is gone I suspect due to the fouled looking spark plugs being changed...
P0204 - Fuel Injector 4 Circuit/Open
P2317 - Ignition Coil 6 Secondary Circuit - Low Ionization

Here are the symptoms:
Rough Idle
Will not rev past 2100/2200 RPM
Past 2200 RPM, the car needle "dances" up and down
Upon listening to injectors, some are clicking rapidly, some are slow and clacky. It's really hard to tell, but I'm assuming it may not be the injector itself given I've cleaned them and ran cleaner. I may replace these if suggested...

Here are my thoughts:
Initially, based on this post: https://www.jeepkj.com/threads/misfire-from-injector-wiring-circuit.69585/ I thought it may have been a wiring issue.
I therefor checked a lot of wires, and don't see any issues.
I may check voltage here soon, unsure on if that's at all helpful.
I feel like a shorted wire would be more obvious, and cause a lot more than two cylinders to basically go down the drain.

Here are steps I have taken to diag/fix this:
Battery Terminal Disconnect for 24 hrs to "relearn" (Done Twice, no help.)
Checked Fuses (All related fuses move power and don't appear burnt)
Swapped Coils 6 and 1 to rule out the coil 6 (Problem persists in cylinder 6)
Cleaned all 6 injectors (Beginning to suspect I should order new injectors...)
Cleaned entire fuel system and switched to Shell 93 for a full tank of driving (No help, just as the injector cleaning)
Inspected wires to/from coil 6, injector 4, and PCM (No damage apparent? Moving the wires did nothing as well, which I believe would not be the case if it was shorting out.)
Swapped Relay for ASD with Lower Rad Fan (No change, rules out ASD Relay Failure)
Pulled, Inspected, and cleaned up all PCM plugs (Ideally hoping the PCM itself isn't going bad, although as many have mentioned on here, that would come with more signs than just a coil 6 low ionization.)

Possible Solutions:
Well, I am considering doing another compression test...
Aside from that, I think new fuel injectors would be another option on my list.
Past that, I have no clue besides outright PCM replacement... Does this require any specialized encoding if I find a 05' donor?

Hoping someone like @Billwill could help?

Click to expand...

Thought did you change fuel filter? Note my 2004 Liberty does not a fuel filter! But a fuel filtercan cause thesse syptoms, clogged screen on the fuel pump could straving motor and give syptoms of miss fires and reving past 2200rpm, I checked Autozone and ssaw a fuel filter, but locate it first!

Xterra4x4 said:

Thought did you change fuel filter? Note my 2004 Liberty does not a fuel filter! But a fuel filtercan cause thesse syptoms, clogged screen on the fuel pump could straving motor and give syptoms of miss fires and reving past 2200rpm, I checked Autozone and ssaw a fuel filter, but locate it first!

Click to expand...

I forgot to add that I changed the fuel filter. This was already done. I'll add it to the list.

Compression testing tomorrow then ordering injectors Friday. Will update.

Did you check the fuel injectors impedance with a meter to see if #4 is open and compare it to the other ones? You could have a bad ignition coil driver in the pcm for the other code - pull the #6 coil out and stick one of the old spark plugs in the end, ground the plug to the engine, and fire it up and see if you have spark. you can also use a computer safe test light and back probe the coil trigger wire to see if the coil driver is working(test light cord needs to be connected to the positive batt terminal).

derekj said:

Did you check the fuel injectors impedance with a meter to see if #4 is open and compare it to the other ones? You could have a bad ignition coil driver in the pcm for the other code - pull the #6 coil out and stick one of the old spark plugs in the end, ground the plug to the engine, and fire it up and see if you have spark. you can also use a computer safe test light and back probe the coil trigger wire to see if the coil driver is working(test light cord needs to be connected to the positive batt terminal).

Click to expand...

As mentioned, I am replacing injectors here shortly.
I don't think taking the injectors out and checking to see impedance is worth time. It's like $40 on eBay for new ones.

I was thinking about the ionization... the spark plugs do have spark, so that is not the issue.
There's new sparks in it now, but the old ones had badly worn diodes.

FCSSensai said:

As mentioned, I am replacing injectors here shortly.
I don't think taking the injectors out and checking to see impedance is worth time. It's like $40 on eBay for new ones.

I was thinking about the ionization... the spark plugs do have spark, so that is not the issue.
There's new sparks in it now, but the old ones had badly worn diodes.

Click to expand...

You don't need to remove the injectors to check them - just have to unplug them. Which spark plugs did you put in?

FCSSensai said:

2nd Tank of Cleaner, no luck.
New Sparks, no luck.... although it seemed to run a *little* smoother, and the misfire codes went away.
Only remaining codes are:
P0204 - Fuel Injector 4 Circuit/Open
P2317 - Ignition Coil 6 Secondary Circuit - Low Ionization
Still suffering from basically falling flat on it's face past 2100 RPM, and idling poorly.

Click to expand...

Which sparks did you use? Gapped to 0.040 exactly? Did you use dielectric grease? 2317 is time for a new CoP. 0204 can only be one of three things: Bad injector ( unlikely), bad or fouled connector (possible), or shorted wires(most likely). the 3.7 uses substandard wires (too small a gauge) with non-heat resistant insulation wrapped with crappy ABS plastic cable wrap. All gets brittle as sits basically on top of the head. Also prone to conductor breakage inside the insulation due tow small gauge and heat.

FCSSensai said:

No smoke.
I do have a small EVAP code that showed once.
Any reason(s) why you're suspecting the PCV Valve(s) from this?

Click to expand...

Sorry about the delay... No smoke is very, very good.

PCVs are only 1 of several contributing factors that influence how the ECM/PCM tells your jets and coils to combust fuel. PCVs only have a recommended replacement cycle of 30K. If they get clogged up, it affects fuel:air mix, which gets picked up by sensors, which influences the PCM, the PCM makes the engine adapt. Could be an easy/cheap fix.

I'm not a pro, so I think of things in relative terms. To me, PCVs are "line-conditioners", which apparently moderate control air:fuel mix... which might subsequently impact sensor readings. There are a couple more items of the same nature:
- Evap Purge Solenoid (could be a marker for your evap code). Very easy to access/replace.
- Intake Air Control Valve (easy)
- I think there is another evap related mechanical item back by the fuel pump, but that is a job for pros.

Then there are sensors. All of the following (reasonably inexpensive) DIY parts can conceiveably impact PCM decisions:
- MAP sensor (need to move the A/C out of the way and be very careful to not drop bolts under the manifold)
- Engine coolant temp sensor (next to the MAP, same cautions apply)
- Throttle control sensor (easy)
- Crankshaft sensor (difficult access, better to have a shop do it)
- Camshaft sensor (difficult access, better to have a shop do it)

***ALL*** of the above items have circuitry (except the PCVs). Inspect all connectors and make sure they are not broken. At 150K the housings will be brittle so be careful. If you can lightly pull on a connector and it simply slides off, you need to get the connector replaced so that it snaps on and stays locked on. If you run into that, let me know which one(s). I have the OEM part #s and wire gauges to do exact match. Note that all of these connectors are shaped differently, and most of the retail parts stores sell pigtails that have the wrong wire gauge. If you buy preassembled pigtails, only buy from Standard Brand (sells correct gauges at a premium price) and confirm that the pigtail is for a specific sensor/etc.

FCSSensai said:

No smoke.
I do have a small EVAP code that showed once.
Any reason(s) why you're suspecting the PCV Valve(s) from this?

Click to expand...

**** CORRECTION **** regarding "...there are actually 3 PCV valves on a 6 cyl..." in my reply above. There is only ***1 PCV***, but there are also 2 ***2 crankcase breathers*** that are found in the middle of two beather tubes that are defined in the manual as "PCV system hoses" (see page 25-18 of the 2003 KJ repair manual). Confusing. So to be clear, (1) there is a thing called a "PCV System", (2) that system is a collection of one actual PCV and a hose from that to the intake manifold, and (3) two breather valves connected to two tubes (one each) called "PCV System Hoses" that run from the manifold resonator to the crankcase through the back of the engine block.

Typically it is not all that hard to diagnose.

Figure out the trouble cylinder. Pull the coil and the plug. If things look ok, just move that coil to another cylinder and see if the problem follows the coil. If it does, it is the coil. If not, it is probably the injector if the cylinder has adequate compression. Trace the injector wiring and make sure it looks good.

First time I had this happen I was a good ways from home and just bought a coil and put on that cylinder. It didn't fix the problem and luckily it only missed bad the one time it set the code. I took that coil back off when I got home because it was still missing a little bit and put it under my seat and it's logged about 100K miles under there I'd guess. I replaced the injector and it ran fine. Later this happened again and I whipped out my coil from under the seat and ended up replacing another injector. So I have had cylinder misfire twice and changed 2 injectors in 250K.

You can unplug all the injectors and ohm for resistance on all of them with a multimeter and see if the problem cylinders injector has an obvious different ohm reading from the others. I have this info written down and stashed somewhere but can't find it at the moment.

Once in a while an injector driver will go out or on the fritz in the computer. That's usually easy to check with a test light while running to see if there is no flashing or the flashing stops intermittently. There is a place in florida that does computers for these. Let me know if it is the driver and I will dig up the name of that place.