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1996 Ford F-350 7.3L Power Stroke
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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.
 

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Have you checked the screen behind the fuel pressure regulator on the fuel bowl. Also sounds like low fuel pressure. What is your fuel pressure. Need to check it with a gauge
 

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1996 Ford F-350 7.3L Power Stroke
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Discussion Starter · #5 ·
Have you checked the screen behind the fuel pressure regulator on the fuel bowl. Also sounds like low fuel pressure. What is your fuel pressure. Need to check it with a gauge
Just ordered a gauge so I’ll get a reading in the next couple days and get back to you!
 

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1996 Ford F-350 7.3L Power Stroke
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Discussion Starter · #7 ·
Alrighty. I have an update!

Got a new CPS pigtail in there and that did nothing. Although, we can now rule that and the CPS (tried 4) out completely.

Throttle unit is coming tomorrow so I can rule that out and tbh, I was noticing some play in that anyways so regardless of whether it fixes the issue, it is probably time to replace.

Today I started the truck up and would give it throttle and every time I let go, it would stall right out (same as before). I tried unplugging the ICP sensor and I couldn't get it to stall! Mess around with the throttle all I wanted and it seemed to catch itself WAY faster and not stall. I understand the theory of unplugging the ICP and it allowing the PCM to revert back to a default oil pressure. However, the ICP sensor is BRAND NEW, has no oil in the plug, and the pigtail has been cleaned and looks intact. So, here are my questions...

  • Is it at all possible that a BRAND NEW Motocraft ICP could be bad out of the box (with no signs of oil in the plug)?
  • Can a truck be driven temporarily with the ICP unplugged?
  • I ordered a brand new Motocraft pigtail from RiffRaff. Before I ALSO order another $140 sensor, is there something else that could be causing things to stall out ONLY when the ICP is plugged in? Or, is that just a black and white sign that the ICP and/or pigtail is toast?

Thanks in advance for all your help! I feel like we are getting somewhere :)
 

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1996 Ford F-350 7.3L Power Stroke
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Discussion Starter · #8 ·
Have you checked the screen behind the fuel pressure regulator on the fuel bowl. Also sounds like low fuel pressure. What is your fuel pressure. Need to check it with a gauge
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?

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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Your ICP just reads pressure in the heads and reports it back to the pcm to tell the IPR what to do. Is the tin nut loose on the IPR. You can unplug the ICP and it will run at a default value.
 

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1996 Ford F-350 7.3L Power Stroke
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Discussion Starter · #10 ·
Your ICP just reads pressure in the heads and reports it back to the pcm to tell the IPR what to do. Is the tin nut loose on the IPR. You can unplug the ICP and it will run at a default value.
The tin nut is tight and the IPR was brand new motocraft one. I quickly tried the old IPR solenoid and it did the same thing with ICP plugged in (stalled).

So here is a reading for both the 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 and then stalls. 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 · #11 ·
The fluctuation in IPR with the ICP plugged in makes me feel like the IPR isn't stuck open but rather being given incorrect information. Am I wrong? When you plug it in it goes right to 12-14% and idles perfectly off the default numbers from the PCM.
 

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Prolly time to start looking at the IDM or PCM. Off hand I can't remember which controls the icp. The idm has been known to get water in it and do crazy stuff.
 

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Discussion Starter · #17 ·
Prolly time to start looking at the IDM or PCM. Off hand I can't remember which controls the icp. The idm has been known to get water in it and do crazy stuff.
The IPR is brand new but wonder if it is bad with those low numbers. any thoughts there?
 

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You vould unplug the ICP and see what happens with your pressure reading. It should stay a constant pressure but you still don't have a verified reading
 

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Discussion Starter · #20 ·
You vould unplug the ICP and see what happens with your pressure reading. It should stay a constant pressure but you still don't have a verified reading
So what you are saying is the fact that the IPR fluctuates (although low) when the ICP is plugged in and defaults to the 14.85 (or whatever) when the ICP is unplugged could mean nothing because this is just what the PCM is communicating and not necessarily a real reading.

I am sort of leaning towards PCM at this point but is it possible that everything else (that I know of) could be functioning properly with he PCM but this specific function (reading the ICP) go bad?
 
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