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Discussion Starter · #1 ·
Hello All,

New to the forum here. Have a daily driver, bought new in 2007 in CA. Has 120,000 miles on it. No mods. Maintenance completed as required. Engine is the 4.7 VIN N (Non flex fuel). Vehicle developed hesitation last summer. Only when hot, the engine would stutter and miss. Winter was fine. I suspected a Throttle Position Sensor, but after reviewing Internet topics, decided to replace TPS, IAC, and EGR. Completed those.

Vehicle was still hesitating, so I needed to have the transfer case and front and rear diffs done, so I decided to bring it to the dealer for the maintenance and to fix the hesitation. After about an hour and a half, the service manager had me come to the vehicle to listen to it misfire through the intake.

Before they were to continue with the maintenance, they let me know about this issue before they performed any, "in case I wanted to trade it in and pick up a new vehicle." I asked what was the problem, and was told that the 4.7 PowerTech was a problem engine and has valve trouble. They have them in all the time to redo the heads. They quoted about $4k for a valve job and $8k for a new short block.

I figured that it was time to send the box to the scrap yard, but I decided, WTH, and bring it home to research. So, research I did. I previously changed the plugs, and tested the coils with an ohm meter before replacing them, so I chalked up those weren't the problem. I looked high and low for a vacuum leak, and could not find one. I placed an ATS EScan on it to see what the thing was doing. High long term fuel trims (13-16). Bank 1 higher than bank 2. More pronounced at idle then under load. The misfire code comes up as random misfire. Mode 6 shows misfires across the cylinders, but none to throw the CEL yet. Fuel rail PSI is at 60. Cylinder compression is good (180-160).

So at this time, I am seriously questioning a valve problem. If it was a valve problem, like when a rocker arm gets thrown (saw that problem online), I would suspect a specific cylinder would be misfiring, and doing so regularly. I ran a fuel injector cleaner on the rail, and water misted the intake to clear the carbon, if that was what was truly sticking a valve. Again, I would suspect a more consistent isolated cylinder problem.

I believe I have a fuel problem. I have 8 injectors on the way to replace the existing ones. I did purchase 2 new O2 sensors, suspecting that maybe they have become lazy in the last 120k. But I cannot get my banana hands in that tight space to undo the electrical connection! So I just tightened them back up. Going to see if a friend can help or find an independent mechanic that can get them done.

Here is my thought process:

* If I had an ignition misfire, I would suspect a rich condition, and negative trims.
* If I had an intermittent valve problem, I would suspect a lean condition, which I have, but I would suspect the trims to go back down when the intermittent problem went away.
* I have an O2 sensor problem which is baselining at a lower voltage, calling for more fuel, but both sensors shouldn't go at the same time (I still would like them changed if I could reach the connectors)
* I have an injector problem, fuel is being called for, but is not being delivered in sufficient quantity. I have injectors on the way. If this doesn't fix it, I am thinking that fuel pressure may not be stable, or volume is not sufficient, and I need to look to the fuel tank for a filter.

If anyone has had similar experience, please let me know your thoughts. Going to try and troubleshoot this to the end. I'll let you know where this goes.
 

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Discussion Starter · #2 ·
I thought an ignition misfire would trip a rich condition, but further research shows that due to the heightened amount of oxygen in the unburnt charge would trick the O2 sensor into believing it was lean (extra oxygen) as opposed to additional fuel in the exhaust...Maybe I have to go back to that. BTW, plugs were changed with OEM Champions, so I shouldn't have a pre-ignition situation...
 

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The only DTC's you have are for random misfires? No others?

The 4.7L and 3.7L (V6 of the same design), they elected to go with an easier to press in valve seat in the aluminum head. That did create problems, but "I think" that was changed on later years production motors to cure the problem. Basically, the valve seat can drop from the head, which would cause the engine to run awful. Usually something like overheating would cause that, in fact I saw speculation that every 4.7L or 3.7L that suffered overheating would almost always suffer a valve seat dropping, (If it was of the earlier production with the easier press in valve seats).

People have had problems with "universal" O2 sensors, which would be 3rd party replacement O2 sensors instead of the OEM sensors from Chrysler. Did you replace the O2 sensors with OEM or a typical auto store "Bosch" O2 sensor?

I "believe", meaning I do NOT know for sure, the O2 sensors are switching sensors, mostly because 99% of vehicles use a switching sensor for O2.

The O2 sensors calibration varies drastically with temperature, one thing that does NOT vary is its switch over point/break point, it will always hit 0.5 Volts at 14.7:1 A/F ratio. (from memory, figures may be wrong). The ramp up to the switch over point varies drastically, the corresponding voltage for 14.5:1 could be 0.6V or 0.85V depending on hot the O2 sensor is, but it will always be 0.5V at 14.7:1 A/F ratio.

So, most cars electronic engine management use a "switching" scheme with the O2 sensor, it basically tries to bracket the switch over / break point to keep A/F within a very narrow band of stiochometric. The engine management looks that O2 sensor returned higher than 0.5 V, it richens the mixture until it sees the O2 sensor return lower than 0.5 V, once its lower it leans the mixture until it breaks above the crossover point. Ideally, your A/F ratio should be going the tinest bit rich, lean every cycle with the O2 sensor switching over the crossover point every cycle. If the O2 Sensor doesn't switch over on the next cycle the computer knows the mixture is off more than just a tiny bit and adjusts accordingly.

An Exhuast Leak prior to the O2 sensors can cause the engine to run rich, air is sucked into the exhuast and is seen as the mixture running lean.

The exhuast prior to the muffler is surging, the cam has overlap and the intake pulse can cause a bit of a vacuum at some rpm's in the pulses of the exhaust. So the exhaust system is NOT at a constant overpressure, it is surges and it will suck air in through leaks which will mess up the O2 sensor.

As well, there should be Upstream and Down stream O2 sensors, the downstream O2 sensors are there to test the Catalytic Convertors. I've been told, but I don't know, that comparisons between upstream/downstream sensors will effect the trim of the fuel. But the upstream sensor is doing the primary feedback of the A/F ratio, so if you have an A/F ratio problem, I would suspect the upstream O2 sensors, but would NOT rule out downstream sensors.

If cylinders are missing bad enough, the CEL will actually flash instead of light constantly, indicating you have a serious problem that could damage the engine if you continue driving. Usually misfires of the nature that raw fuel and air is being pumped into the exhaust, you get a flashing CEL.

If you have a dropped valve seat, I "would think" you can buy two rebuilt cylinder heads and replace them yourself for far less than $4k, if you're capable of replacing the heads on a motor.
 

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Discussion Starter · #4 ·
Thank you Mongo,

Sorry I hadn't replied so quickly. A lot has happened since, but not car related. I did have a DTC for an open on Injector #4. I did replace all 8 injectors to see if that was the problem. The issue did not go away.

I hadn't yet replaced the O2s. There are 4, and the plugs are very difficult to access. I can actually loosen the sensor from the exhaust, which I thought would have been my major problem. When I checked them on the scan tool, they are toggling, after LTFT is brought up to about 10-12%

I could do the heads myself. I am at odds with Chrysler for invalidating my "Lifetime" warranty, so I don't want to go too deep into the engine if I prevail in that, but if I have too, I may. If that is the case, I'll by a beater for a 2nd car and just rebuild the engine. Might as well put new rings in and get the walls honed (hope it is as easy as a Ford 460, my last rebuild, LOL!)

I may have a mechanic try to find a vacuum leak. I can't find one, but it sure acts like there is one...Maybe I need to replace the PCV valve.
 

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Same problem

Hi wawoodwa, I'm having the same problem with my '07 4.7l. I am not as mechanically knowledgable as it sounds like you are, so I'm hoping to learn from your process of elimination. Have you found what's causing the problem yet? I'm almost ready to just sell/trade this thing, but I love the vehicle... When it works. I've taken it to 2 different Jeep dealer service departments and 2 different Firestones. Obviously none of them fixed the problem. The codes found were: PO300, PO205, and PO206. Random misfires and injectors 5 and 6. They said all the spark plugs were fouled, so I had them go ahead and replace them. Problem not fixed. Please post if you ever get your figured out and resolved. Thanks
 

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Discussion Starter · #6 ·
Hey JoBurgin,

I actually have a lot of updates. First, I was able to convince Jeep to honor my Lifetime Powertrain Limited Warrany (LPLW). I didn't want to go any further myself without seeing that to the end. Kudos for Jeep for standing up and doing the right thing. I was about to turn the family into Chevy only, which would have been devastating for my wife as she has only ever owned Jeeps. They saved our family as a customer. They reinstated the warranty.

Once Jeep did so, I returned the vehicle for service and to be diagnosed again. They ran it through the paces...compression tests, leakdown tests, etc. They didn't get any mechanical reading that said the valves were the problem, but it was the mechanic's best guess. Jeep did authorize the warranty repair and they replaced the heads with new ones.

Luckily Jeep handled it as part of the LPLW, otherwise I would have been out $4,500. As soon as we gathered the Commander back, I let my wife use it to run errands. On the second startup, it began again. Sputtering, missing, stalled once. No CEL, but same symptoms. Remember, this only happens after the engine is hot and the outside air temperature is hot.

So I called the dealership again and said the head replacement didn't fix it. I called Chrysler and let them know the same. I told the dealership that I was going on a weekend trip with the family and that I would drop it off and let them diagnose again. Basically, give them some time with it to really find the problem.

On our drive back, I called the dealership to see what they have found. My Service Advisor said the mechanic looked at it and told him it "was running like a top." I said I can send him the videos my wife took of the RPM hunting around, dropping to 300 RPM, etc. He said, you know, I'll take it out and drive it.

The next day late in the afternoon, I get a voicemail. "It misses all over the place! We are looking into it." I called the Service Advisor back. He told me he took it out and had to drive home, it was running perfectly and said he didn't know what to do. Customer says it is broken, but it isn't. Then he jumped back in and started driving. It hiccups. He heads to the gas station, gets a drink, comes back in to drive it back to the dealership. Then it really starts acting up. Bucking, jumping, almost stalling. He told me he got it back to the shop and had the Service Manager put his hand on the wheel and he confirmed the miss. Then he gave me a call (Kudos to the Service Advisor and Service Manager!).

He let me know that they were going to work on it. The next day they said they have the problem. It is the PCM. When it was cold, they were able to start it, grab the wiring harness, and wiggle it. It started missing all over the place. They move it back, it was fine. They could now do it at any time. Injectors were firing when the valves were closed, spark not firing at the right time, etc.

They replaced the PCM. (Just a note, the PCM is covered under the 8 year/80,000m emissions warranty, so if you are under that, you should get it free, regardless of ownership). I just received it repaired just this week on Tuesday, and promptly parked it at the airport. It should get some use this Tuesday, and we should see if it behaves the way it used to. Of course, the air is getting colder, so we will see if it is truly fixed if we get another set of hot weather. However, they were 100% confident the PCM was the problem as they were able to do it on command by wiggling the cables and connectors.

If this does fix the problem, most likely there is a bad solder joint or something in the PCM and it loses connectivity when it gets hot. We will see how it behaves this coming week.

I hope this helps!
 

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Sorry for such a late response. Thanks so much for that response. Have you had any more misfires? I'm in TN so with the cold weather, mine has been running perfectly fine. I'm trying to sell it at the moment, but I've got to be honest with the person who buys it. I'd love to fix it before it pass it along to someone else. Do you think the new PCM fixed it? Thanks again.
 

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Discussion Starter · #9 ·
Hello!

We have not had one misfire since the replacement. We too live in TN, right outside of Memphis. Of course, we had a cold snap right at the end of October, so it was the time of year where the problem would previously go away.

The vehicle has been driven hard, but the misfire hasn't reappeared. We are at the point where we trust the car, or at least the misfire is an afterthought. However, we won't really know until summer next year.

I hope this helps.
 

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Discussion Starter · #11 ·
June 2015 Update

Hello All,

I just wanted to give a quick update on this repair. It has reached over 90 for a long stretch here in the Memphis area. Typically, the Commander would have been misfiring for a month or two by this time. The vehicle has been running perfectly.

My wife has even made the statement that sometimes she thinks the engine has stopped when idling as it runs so smooth. Previously, it would shake and shudder, then quit.

I would say this repair has fixed the problem.
 

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Hey JoBurgin,

I actually have a lot of updates. First, I was able to convince Jeep to honor my Lifetime Powertrain Limited Warrany (LPLW). I didn't want to go any further myself without seeing that to the end. Kudos for Jeep for standing up and doing the right thing. I was about to turn the family into Chevy only, which would have been devastating for my wife as she has only ever owned Jeeps. They saved our family as a customer. They reinstated the warranty.

Once Jeep did so, I returned the vehicle for service and to be diagnosed again. They ran it through the paces...compression tests, leakdown tests, etc. They didn't get any mechanical reading that said the valves were the problem, but it was the mechanic's best guess. Jeep did authorize the warranty repair and they replaced the heads with new ones.

Luckily Jeep handled it as part of the LPLW, otherwise I would have been out $4,500. As soon as we gathered the Commander back, I let my wife use it to run errands. On the second startup, it began again. Sputtering, missing, stalled once. No CEL, but same symptoms. Remember, this only happens after the engine is hot and the outside air temperature is hot.

So I called the dealership again and said the head replacement didn't fix it. I called Chrysler and let them know the same. I told the dealership that I was going on a weekend trip with the family and that I would drop it off and let them diagnose again. Basically, give them some time with it to really find the problem.

On our drive back, I called the dealership to see what they have found. My Service Advisor said the mechanic looked at it and told him it "was running like a top." I said I can send him the videos my wife took of the RPM hunting around, dropping to 300 RPM, etc. He said, you know, I'll take it out and drive it.

The next day late in the afternoon, I get a voicemail. "It misses all over the place! We are looking into it." I called the Service Advisor back. He told me he took it out and had to drive home, it was running perfectly and said he didn't know what to do. Customer says it is broken, but it isn't. Then he jumped back in and started driving. It hiccups. He heads to the gas station, gets a drink, comes back in to drive it back to the dealership. Then it really starts acting up. Bucking, jumping, almost stalling. He told me he got it back to the shop and had the Service Manager put his hand on the wheel and he confirmed the miss. Then he gave me a call (Kudos to the Service Advisor and Service Manager!).

He let me know that they were going to work on it. The next day they said they have the problem. It is the PCM. When it was cold, they were able to start it, grab the wiring harness, and wiggle it. It started missing all over the place. They move it back, it was fine. They could now do it at any time. Injectors were firing when the valves were closed, spark not firing at the right time, etc.

They replaced the PCM. (Just a note, the PCM is covered under the 8 year/80,000m emissions warranty, so if you are under that, you should get it free, regardless of ownership). I just received it repaired just this week on Tuesday, and promptly parked it at the airport. It should get some use this Tuesday, and we should see if it behaves the way it used to. Of course, the air is getting colder, so we will see if it is truly fixed if we get another set of hot weather. However, they were 100% confident the PCM was the problem as they were able to do it on command by wiggling the cables and connectors.

If this does fix the problem, most likely there is a bad solder joint or something in the PCM and it loses connectivity when it gets hot. We will see how it 6 ehaves this coming week.

I hope this helps!
Please keep me posted on your situation. I have had the PCM replaced on my 2006 two times and I am still having the problem. I am not a mechanic but I have been a bench tech for electronics. I am concerned the dealer replaced the PCM because wiggling the harness cause the problem. My training tells me the harness is the problem. However my issue is so intermittent the garage has not been able to duplicate the stumbling. I think I may first, have them pull the PCM and clean the contacts. If that doesn't fix the problem then have the harness replaced. (it may cost more than the PCM) This is our second 2006 Commander and the first had confirmed wiring harness issues.
 

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Please keep me posted on your situation. I have had the PCM replaced on my 2006 two times and I am still having the problem. I am not a mechanic but I have been a bench tech for electronics. I am concerned the dealer replaced the PCM because wiggling the harness cause the problem. My training tells me the harness is the problem. However my issue is so intermittent the garage has not been able to duplicate the stumbling. I think I may first, have them pull the PCM and clean the contacts. If that doesn't fix the problem then have the harness replaced. (it may cost more than the PCM) This is our second 2006 Commander and the first had confirmed wiring harness issues.
@johnjet6 This is a 7 year old thread and wawoodwa has not been active on the forum in 6 years, so you probably will not get a reply. Please check dates before commenting in a thread. To see when someone was last active put your cursor on their name. Also, please make an introductory post in the New Member Section. Thanks.
 
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