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2006 Jeep Commander Limited 4.7 V8
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Discussion Starter · #1 ·
Hi all!

I'm still new to the Commander - I purchased mine as a project two weeks ago, and it's running rough. I have a 2006 Commander with the 4.7 V8 and QTII. 189,000 miles.

I have a code reader, and was getting a P0300 (random misfire), and bad O2 sensor codes for 3 of the 4 sensors. Here's what I've done to try to diagnose the issues.

Through trial and error, I found out that cylinders 1 and 7 (front and rear cylinders on the driver's side) are not contributing to the engine running. I pulled the power wire going to the ignition coil on plug, and got no change in RPM at engine idle.

I swapped the ignition coils with cylinders 3 and 5, which were running good.. No change.

Did a compression test on cylinders 1,3,5 and 7 (120 PSI, 135 PSI,135 PSI,120 PSI) This is only a 12% difference in cylinder compression. Based on a compression ration of 9.0:1, the actual compression spec in the manual should be 132.26 PSI, so I'm guessing mu gauge isn't perfect, but it's close enough.

I replaced all 8 spark plugs - 1 and 7 were very black/sooty. The rest looked good.

I did a fuel pressure test - 59 PSI at the fuel Rail, which is exactly what he manual calls for.

Checked and cleaned fuel injectors on 1 and 7 - no change.

Swapped 1 and 3 injectors and 5 and 7 injectors - no change.

Checked for vacuum leaks - no leaks, and there is 13-14 in Hg at the throttle body while idling.

Sprayed carb cleaner around the heads at the base of the intake to see if there was any intake leaks - no leaks found.

Checked MAP sensor readings against actual vacuum gauge reading - good.

I have removed the injectors and put an endoscope camera into the injector hole to see if the intake valves are opening - they are all opening.

I have also checked for voltage at the fuel injectors at cylinders 1 and 7 with a NOID light tester set - the light lit up, so I'm assuming the voltage is good.

I have also cleaned the battery terminals and ground lugs that attach to the body and engine.

Short of a timing issue on just those two cylinders, I can't figure out what I'm missing. Anyone run across a similar issue, or does anyone have an idea of what I should try next?

Thanks for reading and thanks for any advice!

-Geoff Barber
 

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2006 Jeep Commander Limited 4.7 V8
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26 Posts
Discussion Starter · #3 ·
Yes. All four O2 sensors are new. I forgot to mention that after changing them, all four are now giving high voltage codes. I figured I would fix the engine issue and then tackle the emissions issue.
 

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I have the same random misfire code, and replaced all plugs, coils, and injectors. Still have the issue. I've also noticed a loss of power. I'm thinking my issue is with the rocker arms. Seems to be a (somewhat) common issue if you search jeep 4.7 rocker arms. I guess what happens is after a while, they don't function as intended, and the cam eventually ends up popping them out of place, and then you get valves not operating. I haven't yet decided if I want to put the work or the time or the money into investigating/repairing.

Please let us know what you find out!
 

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2006 Jeep Commander Limited 4.7 V8
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26 Posts
Discussion Starter · #5 ·
I have the same random misfire code, and replaced all plugs, coils, and injectors. Still have the issue. I've also noticed a loss of power. I'm thinking my issue is with the rocker arms. Seems to be a (somewhat) common issue if you search jeep 4.7 rocker arms. I guess what happens is after a while, they don't function as intended, and the cam eventually ends up popping them out of place, and then you get valves not operating. I haven't yet decided if I want to put the work or the time or the money into investigating/repairing.

Please let us know what you find out!
I have an endoscope camera with a 5mm tip that fit into the fuel injector hole with the injector removed. With the ignition wires removed from all of the coils, I put the camera into the injector hole and was able to see the intake valve moving on each of cylinders 1,3,5, and 7 (one at a time) while I turned the engine over with the starter. Unfortunately, there's no easy way to check the exhaust valves for movement without removing the exhaust manifold or the valve cover.

I'll keep looking for solutions - Next place I'm going to look is the ground wires from the ECM to fuel injectors #1 and #7.
 

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2006 Commander 3.7 V6, 4WD QT-I
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91 Posts
I would say the 4.7 is the least reliable block that is offered for XK.
 

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169 Posts
So many posts on this forum about trouble with aftermarket O2 sensors... This is just the first one I came across --> Oxygen Sensor Replacement
 

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2006 Jeep Commander Limited 4.7 V8
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26 Posts
Discussion Starter · #10 ·
So many posts on this forum about trouble with aftermarket O2 sensors... This is just the first one I came across --> Oxygen Sensor Replacement
Hmmmm..... Interesting. I think I'm also fighting some electrical issues even prior to the O2 sensors, but I will definitely keep this in mind!
 

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2006 Jeep Commander Limited 4.7 V8
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26 Posts
Discussion Starter · #12 ·
I replaced with NTK, and occasionally get "unexpected performance " codes.
Eventually, I'll swap them out with mopar.
Good to know! I didn't buy the cheapest O2 sensors on Amazon, but they're definitely not the Mopar sensors.
 

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Dallas TX
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658 Posts
Any other issues of note? the pcm unit has an expiration date, so far it doesnt sound like that but asking to see. you may go through and use contact cleaner on both the coil pack, injector side and the ECU plug side just to see if there are any changes.
 

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2006 Jeep Commander Limited 4.7 V8
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Discussion Starter · #14 ·
Any other issues of note? the pcm unit has an expiration date, so far it doesn't sound like that but asking to see. you may go through and use contact cleaner on both the coil pack, injector side and the ECU plug side just to see if there are any changes.
I just had the PCM off last night. I cleaned the ground strap to it, and cleaned the grounding surfaces and the bolts on the inner fender. All of the pins and contacts in the connectors are clean, as well. I didn't see any kind of dates or anything like that - just a part number stamped into the bottom side of the case.

Two things to add -

While I do have 59 PSI at the fuel pressure rail while the engine is running, the fuel pressure drops to 20 PSI within about a minute to a minute and a half of the key being turned off.

As of last night all four of my O2 sensors are showing (P0132, P0138, P0152, and P0158) "O2 sensor circuit High Voltage", and I'm once again getting the (P0300) Random/Multiple Cylinder Misfire Detected.

The odd thing is that the CEL would flash while driving, but then completely go out when I stopped at a stop sign. It's so weird!
 

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2006 4.7L
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200 Posts
I just had the PCM off last night. I cleaned the ground strap to it, and cleaned the grounding surfaces and the bolts on the inner fender. All of the pins and contacts in the connectors are clean, as well. I didn't see any kind of dates or anything like that - just a part number stamped into the bottom side of the case.

Two things to add -

While I do have 59 PSI at the fuel pressure rail while the engine is running, the fuel pressure drops to 20 PSI within about a minute to a minute and a half of the key being turned off.

As of last night all four of my O2 sensors are showing (P0132, P0138, P0152, and P0158) "O2 sensor circuit High Voltage", and I'm once again getting the (P0300) Random/Multiple Cylinder Misfire Detected.

The odd thing is that the CEL would flash while driving, but then completely go out when I stopped at a stop sign. It's so weird!
Another post here mentions a ground strap from the frame to the exhaust system.
Maybe a high resistance in the ground loop causing weird O2 voltages?
 

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Premium Member
Dallas TX
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658 Posts
hmm, i cant get my data log, but all four being the same is a little suspicious... not certain but from what i have seen the fronts are similar and the backs are similar but not front to back.

does anyone else have this info from their commander?
 

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2006 Jeep Commander Limited 4.7 V8
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26 Posts
Discussion Starter · #20 ·
Hi All!

A bit of an update. After exhausting pretty much every electrical test I could think of, I decided to bite the bullet and remove the valve cover on the left side. Lo and Behold, I found the exhaust valve rocker was out of place for cylinders 1 and 7! The Valve lash adjusters didn't feel like they had excessive play, but I ordered replacements anyway. I'll have them and a new valve cover gasket this afternoon!
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