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Discussion Starter · #1 · (Edited)
Hey everybody,

At a loss here :(

1996 Ford F-350 7.3L PowerStroke (Automatic) - 200,000 miles

I am having what is a relatively common issue when CPS sensors go bad. However, I have tried three NEW Motorcraft sensors and have had no luck. Basically, when I come to a stop OR when I am in park and step on the throttle and come off it quick, the RPM drops to around 500 and then either stalls out or grabs itself. I just had it at the Ford dealership and the tech (who I really do trust and knows his stuff) was at a loss. He just did the front timing cover seal and when he had the engine out, the torque converter was painted and brand new. I also think that since it does it while parked, we can probably rule that out as getting hung up.

BRAND New (all OEM/Motorcraft)
  • All 8 Injectors (Stock), this week
  • Fuel Bowl
  • Fuel Lines
  • Oil Lines
  • HPOP
  • Front
  • Timing Cover Seal
  • BARO Sensor
  • ICP Sensor
  • EOT Sensor & pigtail
  • IPR (No rebuilt), new
  • ECT Sensor
  • EBP Sensor Tube
  • Alternator is reading fine
  • Both tanks of fuel are full and sending units are working fine

- It pulls no error codes when he had it hooked up. Previous owner had a TPS Tuner in there that we took out.

The only thing that came up weird in any of the scans was that fuel trim were both stuck reading 200%, which obviously makes no sense.


this is what it looks like when I park and I run the throttle and then let it go suddenly. Dropped right off and stalled.

 

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Both tanks of gas are full and sending units are working fine
I hope you meant FUEL, not GAS.
The only thing that came up weird in any of the scans was that fuel trim were both stuck reading 200%, which obviously makes no sense.
I've never seen anything related to "fuel trim" on a scan for a 7.3L. :unsure:

You might take a good look at the wiring for the IPR and/or ICP. Beyond that, I'm just guessing.
I looked at your youtube link, but it's hard to follow.
 

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Discussion Starter · #3 ·
I hope you meant FUEL, not GAS.

I've never seen anything related to "fuel trim" on a scan for a 7.3L. :unsure:

You might take a good look at the wiring for the IPR and/or ICP. Beyond that, I'm just guessing.
I looked at your youtube link, but it's hard to followo.
yes. FUEL haha thank you
 

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Discussion Starter · #4 ·
I hope you meant FUEL, not GAS.

I've never seen anything related to "fuel trim" on a scan for a 7.3L. :unsure:

You might take a good look at the wiring for the IPR and/or ICP. Beyond that, I'm just guessing.
I looked at your youtube link, but it's hard to follow.
It really seems like a CPS issue where it is rough idling and just stalling when the rpm drops. Maybe I need to take a look at the different pigtails.

idk what the first mechanic was talking about with the “fuel trim” but he was showing me with his scanner.
 

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Discussion Starter · #6 ·
You might take a good look at the wiring for the IPR and/or ICP. Beyond that, I'm just guessing.
I looked at your youtube link, but it's hard to follow.
I got a new ICP (crappy napa one) and put it in and same thing happens as the Motocraft one. If it is plugged in, the truck dies right out from RPM drop sitting int he driveway. If I unplug it, idles fine and no stalling.

I think it is narrowed down to either the pigtail (which seems completely intact, although it was previously oily when I changed out the original ICP OR I am wondering if my PCM is bad and it isn't actually reading the ICP sensor when it is plugged in.

Do either of those seems plausible? Is there a way of testing either the PCM reading the ICP sensor or the ICP pigtail before I dig into either of those? With the icp plugged in, I got anywhere from .8 to 1.3 volts for the ICP sensor depending on how much throttle. Let off the throttle and it sputters and basically stalls out. Would those readings rule out an issue with he pigtail? Or could it still be bad?

What about the IPR? Is that something that could be impacted by the ICP being plugged in or not?

I know there was a 6-position tuner in the PCM and when I took it out I did notice some moisture and corrosion on a couple of the terminals...
 

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Discussion Starter · #7 · (Edited)
So here is a reading for both he ICP plugged in and then unplugged. The one on the left is with it plugged in. Looks like the IPR fluctuates quite a bit and dips when it gets throttle. The one on the right is the ICP unplugged. IPR stays right at 12-14% with throttle. Appreciate all the help with this. I am not sure what these numbers are telling me but learning! haha

 

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Discussion Starter · #8 ·
Replaced the ICP pigtail and it did exactly the same thing plugged or unplugged.

I am really leaning towards the PCM not properly reading the ICP when it is plugged in and thus, miscommunicating the pressure to the IPR. The IPR seems to fluctuate and not be stuck, its just going to the wrong numbers. When it is plugged in, the PCM defaults to about 12-14% IPR and it runs just fine. Is that possible, am I on the right track?
 
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