Fuel trim?

PCM has no idea what the fuel is doing. It only sends signal to IPR to do it's thing. That's a very low level explanation.

What does ICP pressure and IPR % do when it dips in RPM?

 

Fuel trim?

PCM has no idea what the fuel is doing. It only sends signal to IPR to do it's thing. That's a very low level explanation.

What does ICP pressure and IPR % do when it dips in RPM?

Yeah, that is totally fair. I also admit that I am learning but obviously no expert. I have FORscan and a Bluetooth scanner that I have used with this truck. Do you know whether I can use that to understand the ICP pressure and IPR%?

 

 

Looks like it could be your idle switch and/or pedal assembly issue. Can you read TPS % when pushing on the throttle?

Should be a idle on/off reading as well.

@Patrick Feeley has posted the ICP and IPR manual pages and should pop up in a search.

In short, the PCM sends a signal to the IPR showing a demanded % for a target pressure from the ICP.

The ICP reading is your HPOP pressure. The IPR % demand is strictly a demand from the PCM so a faulty IPR is not easily detected unless you manually check it. Those procedures are on the forum but it looks like a idle switch/pedal assembly issue.

 

Looks like it could be your idle switch and/or pedal assembly issue. Can you read TPS % when pushing on the throttle?

Should be a idle on/off reading as well.

@Patrick Feeley has posted the ICP and IPR manual pages and should pop up in a search.

In short, the PCM sends a signal to the IPR showing a demanded % for a target pressure from the ICP.

The ICP reading is your HPOP pressure. The IPR % demand is strictly a demand from the PCM so a faulty IPR is not easily detected unless you manually check it. Those procedures are on the forum but it looks like a idle switch/pedal assembly issue.

interesting. I never thought of those! I can get you the TPS% today.

this would probably do the trick though, right?

 

Could be the Idle Verification Switch (IVS) is getting flaky and tripping at the wrong percentage - or unreliably
it is just one of those little clicker switches (micro switch), they wear out over time - or sometimes get dust inside on the contacts

 

You can run the TPS test with the engine off.

Looks like the idle switch is working but need to see TPS % with it.

 

You can run the TPS test with the engine off.

Looks like the idle switch is working but need to see TPS % with it.

I think that is what the APP is, no? TPS % doesn’t come up with anything

Throttle:

no throttle: reads 10.35%

 

You are correct. Interesting it shows 10% at idle.

 

yeah, I was doing some searching but couldn’t find what % that should be with no throttle/idle

Is it supposed to be 0%?

 

I am not 100% sure on the voltage reading at 0% throttle.

There may be a conflict between the idle switch and TPS but it's hard to tell without watching the data and listening to the motor.

 

I am not 100% sure on the voltage reading at 0% throttle.

There may be a conflict between the idle switch and TPS but it's hard to tell without watching the data and listening to the motor.

I ordered a new CPS pigtail and a new throttle pedal with sensors. The CPS sensor had lost that rubber fitting when I just checked it and it looks like the newer pigtail from riffraff fits a little tighter. Should come in the next couple days so I can rule those two things out. I am also getting a fuel gauge to check fuel pressure.

once I get the pigtail and throttle pedal assembly replacedI’ll take a video of my Phone with FORscan running so we can also hear engine and see gauges.

that sound like good next steps?

 

@Hydro and @White95f250

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

 

When ICP is unplugged it defaults to a certain value so it can still mask the idle switch issue if that's the case.

Is the new pedal assembly installed?

 

Oh interesting. Never thought of that!

Throttle assembly is being delivered today so I’ll get that in and keep you posted.

thanks!

 

@Patrick Feeley should have ICP test produre.

 

although, if the icp being plugged in changes things at all (even for the worse) that would mean the pigtail itself is working. Right?

so when the icp is plugged in, it’s being read, but not correctly. The icp itself is good (tried two), the truck runs fine without the icp, the pigtail is good because the pcm is recognizing that it’s plugged in. It’s just not reading it correctly.

could that be the PCM and if so, is there a way to test that it’s the pcm?

thanks again. I feel like we are getting super close!

 

Are you able to read sensor voltage on the ICP sensor ?

The PCM uses voltage to convert to a "pressure" reading for your convenience (computations are based on voltage numbers, not pressure) -- you can see the default "pressure" that the PCM uses with the ICP sensor disconnected, then compare to connected voltage

 

so with the ICP unplugged, the voltage was 0 with the key on and the truck idling. No stalling.

with the icp plugged in, I got anywhere from .8 to 1.3 depending on how much throttle. Let off the throttle and it sputters and basically stalls out.

no clue what these are supposed to be.

 

I am pretty fluent in 6.0, not as much in 7.3 parameters
the voltage looks about right it we were talking about a 6.0
the systems are very similar, so I would think those are in the ballpark

I see you have replaced the IPR valve, how tight did you toque the valve ?
really sounds like a "lazy" IPR valve that is not reacting quick enough

You could graph the ICP desired vs actual if the 7.3 system has that option
and see if they track as the engine tries to die
Also graph the IPR to compare with the ICP graph -- they should track

 

I am pretty fluent in 6.0, not as much in 7.3 parameters
the voltage looks about right it we were talking about a 6.0
the systems are very similar, so I would think those are in the ballpark

I see you have replaced the IPR valve, how tight did you toque the valve ?
really sounds like a "lazy" IPR valve that is not reacting quick enough

You could graph the ICP desired vs actual if the 7.3 system has that option
and see if they track as the engine tries to die
Also graph the IPR to compare with the ICP graph -- they should track

i mean I torqued IPR to spec and and the tin nut is on tight. Would the icp being plugged Or unplugged cause the ipr to work or not work? Cause remember, if I unplug the icp it runs great and won’t stall. Plug it in, it stalls when rpm drops suddenly.

 

Maybe the IPR isn't responding as it should is my thought also.

 

Sometimes the IPR is cranked too tight just because of the large socket used -- only needs to be 20-30 pounds
any tighter can distort the threads and bind the valve - yours may not be that case, I had to ask

May be worth the time to remove the IPR and either swap in a different one for a test, if you have one available

 

Hmm…

I can try and pick one up tomorrow and try. Although, do any of these scans help show that the IPR is working and numbers are in spec? This is what it looks like when the trucks stalls.

FORscan RPM drop

Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube.

youtube.com

 

That last graph i not voltage -- should be from 0-5 volts
anyways, if you look at the IPR graph it is commanded up, but the ICP pressure is still down -- they should track
May want to add an RPM line so we can see when the engine stumbles

The IPR value is a command - does not mean the IPR is following those commands -- the ICP sensor is the only feedback we have to verify what the IPR actually is doing -- for sure looks to me like the IPR is not following commands

 

okay. That makes a lot of sense! I’ll get some readings tomorrow. As for the dashboard, I’ll get RPM, ICP (volts),IPR%, ICP(kPa) and then get a recording with both the CPS plugged in and then unplugged.

should that get us something to work with?

What keeps hanging me up is that everything I keep reading says that if you unplug the ICP and it runs better, it’s an issue with the ICP being read.

 

Here's the ICP Introduction. Cheers!

 

Those kPa readings really crank my old brain, would be nice to go into options and set that to Imperial

Disconnecting the ICP is really just a band-aid test , for a shorted / failed sensor
I don't recommend that for testing anything but the sensor -- what it does is make the PCM use default numbers internally, this can lead to false interpretation of the problem

 

@Hydro @Patrick Feeley @White95f250

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

 

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?

 

Not sure. For reference, here is what my Cali 97 reads at KOEO and idle. The reference voltage is off for some reason (it's double that value if I measure it with a DVOM) and my BARO is a little lower since I'm at 4100 ft elevation. Cheers!

 

From what I saw in the video it doesn't look like the IPR is demanding more pressure when it comes to the stall. Almost like it's stuck at 14% when it should climb to 50% at least during that occurence.

Live data tells us what the PCM is seeing from the ICP and what it demands from the IPR. In short, ICP(HPOP) pressure is the feedback from the IPR demand. Interesting to see and i'll have to sit down and research it some more. Doesn't seem right.

I watched the video a few times but maybe @Hydro @1Dieselman and @Jimmy's Pilot Service can take another look and see if i'm in the ballpark.

 

Well the one on the right is with the ICP unplugged so it’s just defaulting to that standard guess of like 14%. I feel like that makes sense doesn’t it? The one on the left is where the ICP is plugged in and the IPR is dropping right down so like 5.5-7% and it doesn’t come back up and stalls. I feel like maybe the PCM is interpreting the data from the ICP incorrectly. Remember, same symptoms with two different new ICP sensors and a new pigtail.

 

What I see is the "normal" % for your engine IPR is 9.3-9.7
there is a short blip up to 13.28, then back down to 6.64% (RPM change ?)
The IPR closed up to raise the pressure but did not open back up enough, so the command % is lower than normal idle
Watching the ICP volts and pressure seem to track pretty close -- but the IPR% does not
The PCM is calling for less pressure (IPR % of 6.64) but the IPR is still providing a higher pressure (ICP graph line)
The PCM called for more oil at the last (14.84) but like @White95f250 mentioned, I would have expected a higher % command
the reaction of the PCM is too slow to force the IPR to close in time
When the injection pressure reaches less than 34 bar, the injector stop pushing fuel
you can see the % command start to rise (14.84) but the system has already shut down

What a wall of text (for me at least)
TL-DR -- I think you have a sticking IPR valve

 

TL-DR -- I think you have a sticking IPR valve

that all makes a lot of sense. I honestly can’t thank you guys enough for all this help. I have been getting super discouraged but I feel like I am SO close to a well running and good shape truck.
So we are leaning more towards the IPR than a bad PCM?

maybe I will take the IPR off and make sure the torque is right again. I know the tin nut is tight.

 

Does your IPR have the edge filter on the tip ?

@White95f250 Do you know what years the edge filter moved from the IPR to the HPOP ?
Can the IPR with edge filter go in the HPOP with internal edge filter at all ?
The IPR is the dump for excess oil from the high pressure pump
Since the IPR % seems too low to what I have read on the 7.3
should be around 16% at idle (lower than the 6.0 system) -- possible the edge filter is restricting the oil flow too much ?

 

Does your IPR have the edge filter on the tip ?

@White95f250 Do you know what years the edge filter moved from the IPR to the HPOP ?
Can the IPR with edge filter go in the HPOP with internal edge filter at all ?
The IPR is the dump for excess oil from the high pressure pump
Since the IPR % seems too low to what I have read on the 7.3
should be around 16% at idle (lower than the 6.0 system) -- possible the edge filter is restricting the oil flow too much ?

I just verified that this is the one that I got from riffraff because I still have the original packaging and the part number matches. It is NOT the one with the edge filter and appears to be the correct one. Looks like edge filter stopped in 1995.5 and this is a 1996. I have an IPR rebuild kit so maybe I will try the old one and rebuild it tomorrow. I only replaced it because it was leaking.

 

94.5-95 was the funky time before the changes in 96.

@Patrick Feeley had a good post with all the changes documented. Here's what I saved..

 

Here's the stuff on IPRs. You'll need to check the engine serial number (pre-SN 187100/post-SN 187099). Cheers!