3.6 Pentastar Misfire on Cylinders 1, 3, & 5

Crazyjoker69 said:
I had same issue a while ago with my other jeep and end up being a broken valve spring on cylinder 3
Click to expand...
Crazy Joker!

When your valve spring broke would it only miss at idle?

I have a 2014 Sahara and only cylinder 3 is missing.

I have been telling the shop for weeks to check the lifter and they keep blowing me off and trying different things.

Any help is appreciated.

-Cole
 
Did you find a good fix mine is doing the same only on number 5 cylinder and I have done a lot of the same things you have done. Thanks
 
MDuncan said:
Hi Folks,

Looking for your expertise.

The problem: Random Misfires on cylinders 1,3,5 - Confirmed with Scanner
The Jeep: 2012 JKU 6-Speed, 108K miles
How long: I've been trying to fix this: 9 months

It's hard to feel the misfire when under throttle, but you can hear and feel the slight misfire trembles when at idle.

What I've tried so far:
- New Spark Plugs: (2 set's - 6 NKG & 6 Champion) Properly Gapped
- New Coils: MSD
- New O2 Sensors (all 4 - both sides)
- New Crankshaft Position Sensor
- New MAP Sensor
- All new Rocker Arms and Lifters on that bank (Cyl 1,3,5)
- New Camshaft Position Sensor
- New Injector on Cyl 5 = No change still misfiring
- New upper and lower o-rings for injectors
- New upper and lower o-rings for Lower and Upper Manifolds

Tests Completed:
- Leakdown Test Showed Normal
- Rotated Coils - No Change
- Rotated Plugs - No Change
- Camshafts inspection - no flat spots found

Additional Modifications Possibly Affecting Performance:
Mishimoto Oil Catch Can
Banks CAI
Odyssey Battery

Additional Fixes Completed on Motor:
- New Oil Pressure Sensor


Friends,
Please help. I love my jeep, and I want to drive it to 300k miles and drop in a Hemi and keep driving it.

(Wave),
Matt
Click to expand...
DId you check for vaccuum leaks? Also the wires for the O2 sensors, check that they are carrying proper current. There is unfortunately a broad range of things that can cause something like this, but you have hit the parts cannon pretty good already. Did you have any belts replaced or do any work that might have affected the timing? If you can find a wiring diagram, you might check the relays and voltages the affect only that one bank. Also, if I were dealing with this, I might get a second set of sensors. Just because a part is new doesn't necessarily mean it's good these days.
 
I'm facing this problem but on bank 2. I have a 2012 with 184k on it. I've only owned it about 10 months so I don't know how long this issue has been going on. Like others I've done a lot of troubleshooting.


Sparkplugs (twice)
coils
compression test
new injectors
smoke tested the intake
new cam and crank sensors
re-seating ECU plugs

In addition to the bank 2 misfires (which are usually at idle) I get an extended crank if the jeep has been heating soaking. If I turn the key to "on" and let it sit a second, it seems to prevent the long start.
 
stephenspann27 said:
I'm facing this problem but on bank 2. I have a 2012 with 184k on it. I've only owned it about 10 months so I don't know how long this issue has been going on. Like others I've done a lot of troubleshooting.


Sparkplugs (twice)
coils
compression test
new injectors
smoke tested the intake
new cam and crank sensors
re-seating ECU plugs

In addition to the bank 2 misfires (which are usually at idle) I get an extended crank if the jeep has been heating soaking. If I turn the key to "on" and let it sit a second, it seems to prevent the long start.
Click to expand...


Is bank 2 on the right side (passenger) side? If so I remember there being a problem with how the wiring harness was routed around over there and it was doing something to the connector ( or it's pins ) causing a issue.

Also are you using OEM parts, i've heard a few times where they weren't used and that was the problem with it not getting fixed.
 
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BLACKJKU said:
Is bank 2 on the right side (passenger) side? If so I remember there being a problem with how the wiring harness was routed around over there and it was doing something to the connector ( or it's pins ) causing a issue.

Also are you using OEM parts, i've heard a few times where they weren't used and that was the problem with it not getting fixed.
Click to expand...
Bank 2 is on the drivers side. I’ve been using oem or name brand parts like Bosch.

I think the "extended crank when hot" and "bank 2 misfires" are two separate issues. I think something I did today made an impact on the misfires, and they seem to be fewer in number (that could always change later, but today was consistent). I reset the ECU using Jscan, and draining power to the ecu and turning the headlights off/on. I also loosened wiggled, and re-tightened the grounds, and reseating the ECU connections again. I also shimmed the ground battery cable to make for a tighter connection.
 
stephenspann27 said:
Bank 2 is on the drivers side. I’ve been using oem or name brand parts like Bosch.

I think the "extended crank when hot" and "bank 2 misfires" are two separate issues. I think something I did today made an impact on the misfires, and they seem to be fewer in number (that could always change later, but today was consistent). I reset the ECU using Jscan, and draining power to the ecu and turning the headlights off/on. I also loosened wiggled, and re-tightened the grounds, and reseating the ECU connections again. I also shimmed the ground battery cable to make for a tighter connection.
Click to expand...

Replacing the junk battery clamps is the better solution for better battery connections.
 
I drove and idled for 30 mins this morning and only have 4 misfires. I think the grounds that are on the inside of the fenders is maybe the issue. It seems to improve everytime I clean those. I'll report back after more driving if the misfire have continued to stay low. They are nowehre near enough to trip a MIL right now
 
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BLACKJKU said:
Don't know if you shop Amazon but they have some good ones, if your not needing extra spots for some auxiliary wiring these are good and can buy anywhere.

[/URL]

Any if you want some extra connection spots these will be good.

[/URL]

[/URL]
Click to expand...
Thanks so much for the help. I ordered the nice sunmorn ones
 
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Similar to what someone else posted on this thread. If I reset the ecu, I don’t get any misfires until the second run cycle. I also found that if I unplug the map sensor, I don’t get any misfires. I assume that open loop is running a richer mixture ? I replaced the map sensor with a new one and had no change. I also have a long crank tilt when the engine is heat soaked. I’ve been thinking about maybe using a programmer, or have someone tune the engine. Maybe richen the mixture at idle.
 
MDuncan said:
Hi Folks,

Looking for your expertise.

The problem: Random Misfires on cylinders 1,3,5 - Confirmed with Scanner
The Jeep: 2012 JKU 6-Speed, 108K miles
How long: I've been trying to fix this: 9 months

It's hard to feel the misfire when under throttle, but you can hear and feel the slight misfire trembles when at idle.

What I've tried so far:
- New Spark Plugs: (2 set's - 6 NKG & 6 Champion) Properly Gapped
- New Coils: MSD
- New O2 Sensors (all 4 - both sides)
- New Crankshaft Position Sensor
- New MAP Sensor
- All new Rocker Arms and Lifters on that bank (Cyl 1,3,5)
- New Camshaft Position Sensor
- New Injector on Cyl 5 = No change still misfiring
- New upper and lower o-rings for injectors
- New upper and lower o-rings for Lower and Upper Manifolds

Tests Completed:
- Leakdown Test Showed Normal
- Rotated Coils - No Change
- Rotated Plugs - No Change
- Camshafts inspection - no flat spots found

Additional Modifications Possibly Affecting Performance:
Mishimoto Oil Catch Can
Banks CAI
Odyssey Battery

Additional Fixes Completed on Motor:
- New Oil Pressure Sensor


Friends,
Please help. I love my jeep, and I want to drive it to 300k miles and drop in a Hemi and keep driving it.

(Wave),
Matt
Click to expand...
 
Good evening, Jim McBride here, similar concern 2015 wrangler 170,000 mi, random misfire code, monitoring misfires while driving indicated slight misfiring that couldnt be felt on cyls 1,3,5 all congruently under slight load, indicating issue due to something common with that bank, performed backpressure test, still almost within spec, bouncing to 3 psi at idle or above in park, on test drive went to 8 psi, compared to left bank , noticed immediatly that although the pressure was similar, up to 3psi in park, the needle hit much harder on the right bank indicating slightly clogged convertor, replaced both convertors and test drove for verification, issue resolved.
 
Hey if anyone else is dealing with this, the resolution for me was a catalytic converter replacement.

Apparently the cat was just clogged enough to cause misfires on bank 1 at idle.

You can test by pulling the bank 1 upstream O2 sensor and if the misfires disappear with it out (decreased backpressure) the cat is the problem.
 
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Hey if anyone else is dealing with this, the resolution for me was a catalytic converter replacement.

Apparently the cat was just clogged enough to cause misfires on bank 1 at idle.

You can test by pulling the bank 1 upstream O2 sensor and if the misfires disappear with it out (decreased backpressure) the cat is the problem.
 
Jmcbrideautoexpert@gmail. said:
Good evening, Jim McBride here, similar concern 2015 wrangler 170,000 mi, random misfire code, monitoring misfires while driving indicated slight misfiring that couldnt be felt on cyls 1,3,5 all congruently under slight load, indicating issue due to something common with that bank, performed backpressure test, still almost within spec, bouncing to 3 psi at idle or above in park, on test drive went to 8 psi, compared to left bank , noticed immediatly that although the pressure was similar, up to 3psi in park, the needle hit much harder on the right bank indicating slightly clogged convertor, replaced both convertors and test drove for verification, issue resolved.
Click to expand...
Hi Jim, just reading your post, it’s interesting.
Can you elaborate on where you connected your pressure gauge in being able to read it on test drive via either cylinder bank? Would the pressure gauge also be the type used for fuel pressure too?
Look forward to getting your reply 👍
 
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