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Discussion Starter · #1 · (Edited)
My 06 died on me while driving. I tried to restart but it wouldn't build sufficient ICP. Towed back home and replaced my IPR valve because I had one. The original IPR valve stuck in the bore but I was able to get it out with a small pick and then I cleaned out all the debris as best I could. Truck started right up after that but ran really rough. I drove it to try and work the air out and sometimes it felt like it was going to die. At idle, my ICP would drop as low as 300 psi sometimes but it never died. I kept trying to drive it and eventually it started running a little better but then it got a little worse again. Just more missing and erratic running. I ended up taking it in to a shop that had testing equipment. They determined that most of my injectors were bad which I was not surprised about as they had 235,000 miles on them. They tested checked the compression on all my cylinders and the lowest was 390 psi. They changed all my injectors and stand pipes and it always starts well but would have a miss until it got warmed up after driving it a lot. The technician wanted to chagne my engine oil just to see what that would do. I had been running a 10w-30 and they changed it to a 15w-40 and after that it has actually run worse. Misses more and always has a slight miss even after its been warmed up. ICP is always within 100-200 of desired and duty cycle ranges from 20% to 85% as they can change it with their scan tools. They think it is a problem with my high pressure pump as there was a debris on my ipr screen when I changed it. I know the 06 hpop are know to be very robust and don't fail very often but just wondering if anyone else has another idea of what could be the issue. It always starts fine and it runs better on a thinner 10w-30 oil than a 15w-40 oil and my icp numbers were very erratic and low after I changed the ipr valve. Neither the technician or I can think of anything else.
 

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I would pull and recheck the IPR valve screen, it may be possible that all of the debris from the first IPR valve change did not get cleaned out and is partially blocking the screen or causing issues with the new valve. That would explain why the thinner oil is causing it to run better.
 

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I run 5w40 Rotella T6 and my truck really likes it. Not that that is the cause of your problem, but it might be better than 10w30 for the engine.
 

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Discussion Starter · #4 ·
I forgot to mention that when they had the truck hooked up to their diagnostic equipment it would run fine. Which makes me think it is an issue with the icp sensor, icp harness or the ipr valve maybe. But they are able to get the truck to make 4000 icp which makes me think an issue with icp sensor. They tried a different sensor off a different truck and it still ran rough. When they unplugged the icp sensor it still ran rough as well.
 

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Having it hooked to diagnostic equipment should not make it run better if it were a mechanical issue. I would lean towards possibly the IPR and have them swap in another valve to check. It is possible you got a bad one. Also, has the FICM been checked for voltage, especially under a load?
 

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Discussion Starter · #6 ·
FICM voltage has read good on my sct unit. Always started well even in the winter not plugged in. I did a lot of thinking about it and I figured it had to be ipr valve or something with the icp sensor but since it doesn't clean up with icp unplugged I think that should be ok. I guess try and IPR and if that doesn't do it bite the bullet and get a new hpop.
 

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Discussion Starter · #7 ·
They took the ipr valve out and the screen was clean on it. They also changed the cam sensor but it made no difference. When they hook it up to their scan tool and turn up the ipr duty cycle a little bit, the idle smooths right out and it runs s great. Is the duty cycle controlled by the ficm?
 

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Discussion Starter · #8 ·
I suggested that they try the ipr valve but the service man was hesitant to try that as he had "never seen that before". Well, they finally just changed it and that fixed all the problems. Runs great now. Going to go pick it up this afternoon. They didn't bill me for all the time they spent trying to diagnose the ipr valve either which was real nice so my bill isn't too much higher.
 

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Sometimes you just get bad replacement parts. Glad you got it fixed.
 
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