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Discussion Starter · #1 ·
Bought a CTS monitor so I could see if my IPR or ICP sensor were causing this problem I have with the truck dying at idle. This is what I got:

At idle IPR% is about 9.5-10.5% and ICP sits around 480-500. Driving around number seems good. Cruising on level ground and going WOT i get about 2700-2800 ICP and 40% IPR duty cycle. Everything I've read makes me think these are fine numbers.

Now occasionaly if I sit at idle, the ICP will drop to 200-350 and the IPR% will fluctuate really bad up and down and the truck idles rough and stalls unless I put my foot in it and then it'll come out of it. Sometimes itll be perfectly fine after that and sometimes it'll act fine then drop again.

I could imagine it's possible for the IPR to work fine when it has the pressure generated with the truck under load and then pherhaps stick and fail when the truck doesn't have a load? Does anyone else think so?
 

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What you're seeing could be from a sticky IPR, but I'd suspect wiring issues at the ICP sensor. If the wires are shorting together or are frayed, it could affect the signal the PCM gets from the sensor. I'd eyeball the pigtail coming off the ICP and replace it if the insulation is deteriorated or you see any other issues.


[On edit] What Nick said (while I was typing). ICP sensor could be suspect also.
 

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To me, the ipr is reacting properly going down the road and the ipr signal on scanner jumps as the ICP starts screwing up at idle.
I look to see if it's old style. tell them they really should update with the new style and it might fix the problem and if it does not there is going to be diag time but why pay diag time first when there is an old style ICP right there that should be updated and the problem maybe gone once installed.
For there I look at wires when I look for 12volts at the ipr positive wire.
If acting like it's getting a flakey or no signal, I go to my ipr. jumper hive it a straight 12volts.
From there I install the test IPR.
Little routine that works for me and makes sense to someone who has to pay or should anyway but I've never met an owner hat was in love with his decade old plus mushroom style ICP. If installing a new style gets the ICP current, reliable and has a very good chance of eliminating diag time costs......
 

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Have you monitored low pressure oil. Reason I ask is when I did my big build, the first set of tunes I used stumbled occasionally at idle, and at red lights it would some times surge forward. What it was is the new injectors needed more idle pressure to be stable. They are big single shots, but same for stocks some times. Stock is about 480ish to 500. I had to raise mine to 585 to stop this issue. What happens is the computer reads the oil pressure is too low at idle, so it surges the motor to bring it up. Once stable its fine. Running at 585 at idle just keeps the low pressure high enough to make it idle smooth. Took a lot of tuning to figure it out.
 

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Discussion Starter · #6 ·
I know I've looked at that sensor about 50 times but can't remember what it looks like for the life of me. I'll have to check the style of it tomorrow. How hard is it to replace the pigtail if it's getting worn? If I have the old style or worn out wires I'll definetly start there.
 

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It's low voltage so you need to use the bare metal crimp butt connectors, heat connector with small handheld butane torch and fill ends with thin solder. Then you slide down the heat shrink that you had slid up the wire about two inches away from that heat and shrink it over repair.
This is what you want before the heat shrink slides down to be shrunk.
 

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Discussion Starter · #8 ·
Well my ICP sensor has the wrench holds around the body of it. So thats the new style correct? And my pigtail doesn't look to be shorting out or have any bad spots anywhere. Also no oil in the ICP.
 

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Discussion Starter · #10 ·
Yeah I'll try cleaning it next. Is riffraff the best place to get the orings from?
 
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