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Discussion Starter #1
I’m having an issue with a low IPR duty cycle percentage. At hot idle my IPR percentage drops way down to about the 15% mark. Everything I’ve been able to gather about the relationship between the ICP sensor and the IPR valve tells me that this is most likely an ICP sensor issue sending an incorrect reference to the PCM, thus the PCM telling the IPR it needs to be wide open. So I replaced the ICP sensor and that didn’t do anything to fix the problem. My next step is going to be to replace the ICP pigtail and see if that changes anything. I’m just confused because the ICP voltage seems to be correct. I am using AE and these are the numbers I got this afternoon after driving home. IPR duty cycle - 15.23%, ICP Voltage - .87V, ICP pressure 577 psi, ICP pressure desired- 580 psi.

The truck is drivable at the moment, although I am trying not to drive it until I get this figured out. The truck will also start to idle very rough about 2 minutes after startup. After a couple minutes of rough idle it will just settle down into a normal smooth idle. This happens about every other time I start it up, doesn’t matter how cold it is outside, sometimes it does it and sometimes it doesn’t. I also have pretty sluggish acceleration which I believe to be related to the IPR. The IPR issue seems to be all the time though.

I have no codes, 65 psi fuel pressure, and 47.5 -48V of FICM.

I’m just really stumped about this IPR thing and hoping that getting to the bottom of it will get my truck running good again. Thanks in advance
 

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Discussion Starter #3
Yeah I did I try unplugging the sensor. The truck starts like that but doesn’t run very well, pretty rough.
 

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CJfisher,

I thought about that too, but wouldn’t I be seeing opposite readings on the IPR as what I have? I think if I had a leak somewhere, I would be seeing an unusually high IPR% because its commanding it to stay closed more to compensate for the leak? I may be wrong in my thinking though.
 

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Discussion Starter #6
So just out of curiosity, how well should the truck run when the ICP sensor is unplugged and it is getting default values? Like I said before, mine runs, but not very well with it unplugged. Is that normal?
 

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To answer your last question, on a normal running truck, disconnecting the ICP will make a small change briefly, but then the PCM will adapt and things should go back to normal...in other words, no real change for a normal running engine. If there is a problem with the ICP, you should get an improvement. However, I'm confused by your first post. Typical IPR is around 21% when idling. Yours being 15 tells me your HPOP is just capable of putting out a little bit more oomph at idle and doesn't need the valve closed as much for the same pressure. Or am I interpreting what you're saying incorrectly?

IMO, you shouldn't have to worry about the IPR or ICP....the numbers look good. Though, I do have to ask if you replaced the ICP with OEM or did you use aftermarket? I've had nothing but problems with aftermarket ones making engines not run or run like crap. Anywa, instead I'd be getting a second opinion on your AE and checking for codes using a different scanner, such as FORScan Lite. People have had issues with AE at times actually pulling codes. I'm thinking you have an issue somewhere else, and disconnecting the ICP is just bringing them to the foreground a bit. In addition to scanning for codes, I would do an injector buzz test and a contribution test. The codes (if there are any) and the results of those two tests might shed a little more light.
 

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It might also be possible that the IPR valve is slightly plugged up (in the pathway to drain).
 

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Discussion Starter #9
Weatherlite- Yes, you are interpreting what I am saying correctly. Normal IPR % should be around 21% or so at hot idle and mine drops to about 15%. The ICP sensor I put in was OEM. I was not aware that others were having issues pulling codes with AE. Does FORscan have the ability to do the cylinder contribution test like the IDS software does? Cylinder contribution test on AE is pretty much worthless. I did do the injector buzz test, and it passed both on the scantool and I got a very good audible click from each one.
 

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Would be a good time to pull the IPR and clean the screen before it splits and the junk goes thru the valve
as @bismic1 mentioned it is likely partially plugged
that would explain the low IPR% readings, since the valve is a drain for the high pressure oil and the PCM is trying to dump more
 

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Discussion Starter #11
Yeah, I agree that hopefully the IPR valve being partially plugged is the issue, makes sense. Tomorrow I will go see if I can pick one up and throw it in. I’ll let you guys know. Thanks for the help so far, I really appreciate it.
 

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It might also be possible that the IPR valve is slightly plugged up (in the pathway to drain).
Good possibility!

Yeah, I agree that hopefully the IPR valve being partially plugged is the issue, makes sense. Tomorrow I will go see if I can pick one up and throw it in. I’ll let you guys know. Thanks for the help so far, I really appreciate it.
I don't know that I'd go that far. I would just get the seal kit with the new screen, pull the IPR, inspect the old screen to see how clogged it is, and then remove it and all the seals. Next, with a mirror (unless you are a contortionist...or have a borescope) take a look into the HPOP cover through the IPR hole. Make sure there's nothing in there. Clean the IPR valve, and since there is suspicion of an obstruction, you'll want to clean "inside" the valve as well. I use CRC QD electronic cleaner spray. It's safe for the soft rubber parts and cleans nearly as well as brake parts cleaner. It's more expensive though, so I only use it when there is worry of contact with plastic, rubber, etc. Anyway, spray it into all of the holes on the sides, and while you're doing that use a narrow blunt object (I think I used a small allen wrench with the rounded tip) and push the spring loaded part of the valve back and forth to flush out any crap in there. The big thing is the holes in the side for this suspected obstruction. Those are where the oil goes when the valve is at idle. The higher the % goes up, the more oil goes through the end with the screen, so if there is an obstruction causing the low IPR numbers, it would be in those holes.

Oh, and as for FORScan lite, I know for sure it will do the buzz test, but honestly I can't remember right now if I used that or another app I use....and that app sucks, so I can't really recommend it. lol I know they were adding it to the lite version, but I can't remember if it ever got done.
 

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Pulled up a video showing what I was talking about with the cleaning of the valve. I think it's around the ten minute mark that he starts cleaning the valve....though the information prior to that is really useful as well.

 

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Discussion Starter #14
Well guys, it looks like it was the IPR. I ended up just swapping it out for a new one. IPR % is holding solid at 23-24% at idle and truck runs great! I did clean out the old one, but didn’t see anything out of the ordinary. The screen looked perfect and there was no debris on it or when I sprayed out the ports. About four years ago when I “bulletproofed” my truck I installed an IPR research metal HPOP screen (pretty much indestructible), so it was nice to see that it has been doing its job as there was absolutely nothing on the IPR screen. Anyways, thank you all for the help getting this resolved, it was much appreciated!
 

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Glad to help. Thanks for closing the loop w/ a posted conclusion.
 

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Appreciate the update. I wonder what the difference between the valves could have been.
 

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I would go straight to a diesel shop and purchase a brand new Alliant Power IPR and pigtail. The coil is on its last leg, and when it finally overheats, the solenoid will pull that screen right through the valve. Also do yourself a favor, and keep a spare one with the appropriate socket in your glove box, along with a spare oil pressure switch, and CMP and CPS. all of these items are frequent failure items.
 

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I would go straight to a diesel shop and purchase a brand new Alliant Power IPR and pigtail. The coil is on its last leg, and when it finally overheats, the solenoid will pull that screen right through the valve. Also do yourself a favor, and keep a spare one with the appropriate socket in your glove box, along with a spare oil pressure switch, and CMP and CPS. all of these items are frequent failure items.
For the 6.0L, the CMP (equivalent to the original failure prone CPS in the 7.3L) and CMK are not frequent failure items.
 
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