ok the nut is there, is there a way to test the ipr? Expa mentioned something about high duty cycles. Can anyone tell me what the normal numbers are for % duty cycle and i will check it out

 

I don't know the exact numbers, but mine was something like 50% and a lot higher while cranking. That means it wasn't getting the ICP it wanted, so it kept asking for more.

Do this test and also a separate test of disconnecting the ICP plug, which will bypass and rule out a failed ICP.

Do you have AE?

 

i don't have AE but i have a dp tuner infinity(i think thats what its called). I can watch the parameters that they have programed on it (which is quite a bit). I think i can also add parameters to the screen but haven't figured that out yet. i can monitor % ipr duty cycle though. Was yours at 50% at idle? or just cranking? should i disconnect the icp sensor and see if the drop at stop rpm symptoms continue? Can i drive the truck safely with this unplugged?

 

If I had the same problem again, this is what I would do.

1. Pull RPM, ICP, DC%, EOT, Battery voltage

2. My ICP was low, so either not making HPO (IPR) or not properly reporting HPO (ICP)

3. Unplug ICP in case it was bad and falsely stopping truck from starting

4. Still no start. Replug ICP back in. Odds are strongly against BOTH the ICP and IPR going bad at the same time

5. Cranks and watch DC%. If HPO isn't climbing enough, the IPR increases and increases, trying to get high enough oil pressure.

6. If it cannot get enough oil pressure to start, either HPOP died (rare) or low oil, wrong oil, or IPR.

Don't forget UVCH and GP related items.

This is all for a NO-START. See Tugly's signature for no-start trouble shooting guide and values

 

The short story is...Yes.

 

okay guys I think it is the AC compressor clutch or pulley going bad .when I turn off the AC the RPMs don't drop too low when I come to a stop. The question is should I rebuild the clutch or just replace the whole compressor since is 17 years old?

 

I also wanted to add that I just recently pulled out a shim because the clutch was cycling too much. Not sure if that has something to do with it or not but the air gap was a little too high so I pulled out the one and only washer

 

I don't think that is the problem. If it ain't freezing up, I would bet on something else.

 

z31freakify was saying that its common, i think. i can literally drive down the road and turn the a/c off and no rpm drop at stop, turn it back on and it does it every time. i guess it could be something else, but just weird how i can turn it off and on like that

 

Hey expa, i checked the ipr % duty cycle and it climbs to 45% during crank up and 11.4% at idle. truck starts right up though and runs fine. a little bit of a rough idle but not to bad. i found that if i turn the a/c off the rpm symptoms clear up

 

bump , anyone ?

 

I've got nothing but a bump for you.

I have this problem on occasion but have not tried turning off the A/C. My truck is down for injectors and cups so I can't test any ideas out.

 

If it's ok with the AC off, and happens reliably with the AC on, that's pretty strong evidence the AC is bad. Not exactly a cheap fix, but if you really need the AC...

The symptom could also come from an overdrive lockup clutch that fails to release. I don't think that's the case here, just throwing it out there for the next guy trolling thru the threads looking for answers.

 

If you have eliminated BOTH the IPR (which "can" cause erratic idling from a load to a coast) AND any Chip or Tune, performed a Road Test logging data a reviewing it, your probably looking at a worn Coast Clutch.

When I say "worn" I don't mean its going to fail tomorrow. I drove a couple a hundred-thousand-miles because I was too lazy to remove the Trans and send them out.

What occurs is as you come to a stop or off the accelerator slowing the RPM's will drop to 400 or 500 before recovering to about 650 RPM's. If this is what its doing, look at the Coast Clutch. Providing you find no anomaly following road tests.

Ps: A/C, P/S, or Water Pump Seized won't hiccup a diesel. 17.5 - 1. I know a guy who got his shirt sleeve caught in one, never bogged down or hiccupped, just ripped his arm off; almost lost his arm. He was out of work for almost two years because of surgery and recuperation. Had it have been a Gasser, it would have stalled. I know a guy who did that as well on a 460 CID Lincoln.

 

False! the AC does affect the engine rpm when an AC compressor goes bad, on Gasser's it's worst it even shuts the engine off.