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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
Check your coil packs,sounds like you may have a couple bad ones.
 

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2006 Jeep Commander Limited 4.7 V8
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Discussion Starter · #22 ·
Check your coil packs,sounds like you may have a couple bad ones.
Coil packs are all good. I swapped them around. I found the exhaust rockers off for cylinders 1 and 7 when I pulled the valve cover off last night. New lifters are here and soaking in oil. They seem to be the failure point from all the videos I watched. I'll reassemble tomorrow, when the weather cools off a bit. It's 95 degrees in my garage, and I don't feel like sweating that much tonight!
 

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06 Commander Limited 4.7 Black
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If those rockers popped off those two cylinders take your borescope and inspect the valve seats very closely on the exhaust valves on those two cylinders.
Not always but generally when rockers are popping off particularly on exhaust valves the seat has dropped down and is holding that valve partly opening allowing too much clearance in the system allowing The rocker to fall off. I just replaced the heads on my second 4.7 motor with this problem. It's always exhaust because that's where all the heat is. Seems Chrysler used just slightly undersized valve seats and if the motor was ever overheated that will cause the valve seats to dislodge.
Good luck let us know what you find with that borescope
 

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2006 Jeep Commander Limited 4.7 V8
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Discussion Starter · #24 ·
If those rockers popped off those two cylinders take your borescope and inspect the valve seats very closely on the exhaust valves on those two cylinders.
Not always but generally when rockers are popping off particularly on exhaust valves the seat has dropped down and is holding that valve partly opening allowing too much clearance in the system allowing The rocker to fall off. I just replaced the heads on my second 4.7 motor with this problem. It's always exhaust because that's where all the heat is. Seems Chrysler used just slightly undersized valve seats and if the motor was ever overheated that will cause the valve seats to dislodge.
Good luck let us know what you find with that borescope
Would the cylinders still hold 120 psi during a compression test if the valves were open enough to cause the rockers to fall out?
 

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Yep I just saw this happen on a YouTube channel can't remember which one it was. The compression test was fair not good, just like yours but the valve seats were pulled down just enough to hold the valve partially open and the rockers to fall off.
Besides doesn't cost a dime to take a close look at the valve seats with the borescope. Compare it to known good cylinders. Guess you could also measure exhaust valve length.
From some place on the head to the top of the valve stem. Same thing compared to known good cylinder.
 

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Discussion Starter · #26 ·
Yep I just saw this happen on a YouTube channel can't remember which one it was. The compression test was fair not good, just like yours but the valve seats were pulled down just enough to hold the valve partially open and the rockers to fall off.
Besides doesn't cost a dime to take a close look at the valve seats with the borescope. Compare it to known good cylinders. Guess you could also measure exhaust valve length.
From some place on the head to the top of the valve stem. Same thing compared to known good cylinder.
Good plan! I like the measurement idea, as I have two good cylinders on the same side! Thanks!
 

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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!
View attachment 44703
View attachment 44702
View attachment 44701
"Out of place"?
You have a gift for understatement.
How did that happen?
 

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2006 Jeep Commander Limited 4.7 V8
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Discussion Starter · #28 ·
"Out of place"?
You have a gift of understatement.
How did that happen?
The valve lash adjusters (commonly referred to as valve lifters) get weak/loose and let the rockers move. Then, the cam just pushes them out. It took me a few different videos on YouTube to find this, but it seemed to fit my problem, so I took off the valve cover and that was the problem! Now the rockers are back in place with new lash adjusters, and the rocker play feels just like the rest of the rockers!
Household hardware Gas Engineering Gear Mass production
 

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The valve lash adjusters (commonly referred to as valve lifters) get weak/loose and let the rockers move. Then, the cam just pushes them out. It took me a few different videos on YouTube to find this, but it seemed to fit my problem, so I took off the valve cover and that was the problem! Now the rockers are back in place with new lash adjusters, and the rocker play feels just like the rest of the rockers!
View attachment 44705
Very lucky nothing else got torn up
 

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Discussion Starter · #31 ·
A little more follow up - As of 10:15 last night, I had the 4.7 back together and running on all 8 cylinders! I took it for a road test, and she runs great, so now I'll be moving on to the O2 sensor issues...
 

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2006 Jeep Commander Limited 4.7 V8
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Discussion Starter · #32 ·
Time for an update!

So I replaced both pre- cat sensors with MOPAR sensors, and They're both reading fine now. I do have a bank 2 fuel system rich code yet, so I'm looking into that.

For the post - cat sensors, I went with the spark plug anti-fouler trick. Bank 2 looks perfect with one of the old sensors, and is in the normal operational voltage, and bank 1 looks great until it gets up to temp. When it's up to temp, the bank 1 sensor 2 goes to high voltage and stays there. I'll try replacing it with one of my other older sensors before I buy another MOPAR O2 sensor...

But, for now, she's going in the right direction, and I'm plinking away at the to-do list!
 
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