Erratic ICP

caladash · Jul 9, 2012

What would cause erratic ICP at idle? Erratic might be a bad choice for words but that's all I can think of! At idle, monitoring ICP with my CTS it bounces from about 460 to 490. The truck will hiccup and when it does ICP drops to a little above 320. The hiccup can barely be felt. It's almost like a miss. Doesn't happen very often and I first noticed it later on in the day on the 4th after an oil change. Running valvoline 15w40. Possible dirty IPR? Any ideas?

907DAVE · Jul 9, 2012

Take a peek at the IPR % to see if the PCM is commanding the drop.

caladash · Jul 9, 2012

Crap...forgot to mention. Percent stayed the same with no changes during idle. I think it was about 10.2 or 8% during idle. Only mod is an intake.

907DAVE · Jul 9, 2012

ICP sensor would be my first guess then.

powerSmokin · Jul 9, 2012

Hmmm seeing your change in ICP makes me wonder bout mine, mine will be at anywhere from 490 to 553 and 12% duty cycle when at idle. I need to get some good tunes, didn't mean to jack your thread.

lincolnlocker · Jul 9, 2012

sounds like bad ipr orings, dirty, or worn out ipr..

TARM · Jul 9, 2012

Think hpop system first then injector wiring next followed by injectors themselves

ICP sensor
IPR dirty,bad oring, loose nut
UVC wiring or wiring between it and IDM
Injector orings or worn injectors

One thing I have learned about IPR DC% at idle is depending on the hpop and injectors, oil used, or tunes it can vary from 6% up to 14% and still have nothing wrong.

Take my sp1 I was concerned when people stated my 12% DC was to high. Then in checking with another member that had the same injectors same builder as well as had my actual pump and then had now a full stealth stage II look thru his records and with both his pumps he ran the exact same duty cycle as I. Tell me that something in the combo was the reason yet when max icp 3100 was called for and maintained DC never went over 43-45% so no pump isue making volume when needed or pressure for that matter.

caladash · Jul 11, 2012

Here's a quick video of it happening. When it gets below 400 for that split second is where the "miss" is felt. Gonna do some inspecting tomorrow weather permitting.

TARM · Jul 11, 2012

Well if you first noticed it after a oil change that would be my first question.

What oil and did you change it or someone else?

Then I would go onto the normal diagnosis for looking for something in the systems gone amiss.

caladash · Jul 11, 2012

Oil was done by me using valvoline premium blue 15w-40.

Peroni · Jul 12, 2012

Caladash I will be interested to see what your problem might be. I've been fighting this very issue going on 5yrs now. Been thru numerious IPR and icp sensors, new connectors even taking the harness apart and replacing the entire wires. Changed pcms, injectors, hpop, pressure tested heads. Checked for cracked pickup tube too. Tried different tuning, live tuning. Can't find anything wrong at all. Stone cold it's fine and usually when fully hot it's ok, but in between most times it has that miss and erratic icp. It's been driving me up the $&#%^@* wall! :cursing:

TARM · Jul 12, 2012

Peroni,

Have you visually checked your oil to see what it looks like when its running like this. Maybe hook a clear hose loop to the HPOP res and see what the oil looks like. See how much air is in it.

powerSmokin · Jul 13, 2012

Peroni said:
Caladash I will be interested to see what your problem might be. I've been fighting this very issue going on 5yrs now. Been thru numerious IPR and icp sensors, new connectors even taking the harness apart and replacing the entire wires. Changed pcms, injectors, hpop, pressure tested heads. Checked for cracked pickup tube too. Tried different tuning, live tuning. Can't find anything wrong at all. Stone cold it's fine and usually when fully hot it's ok, but in between most times it has that miss and erratic icp. It's been driving me up the $&#%^@* wall! :cursing:

The type of oil you may be running might be an issue, I switched to schaffers and it mellowed it out. Did the Molybond X 200.

Peroni · Jul 13, 2012

Have you visually checked your oil to see what it looks like when its running like this. Maybe hook a clear hose loop to the HPOP res and see what the oil looks like. See how much air is in it.

I put a couple sight glasses in a spare hpor and checked for bubbles. Saw a few small ones, put in a Melling oil pump and they went away. Ran better but still has its retard moments.

The type of oil you may be running might be an issue, I switched to schaffers and it mellowed it out. Did the Molybond X 200.

I have tried Rotella, Delo, Mobil, Valvoline, Cat, John Deere and Schaeffer oils. I've tried 15-40, 5-40, 10-30 as well as straight 30 and 40. Schaeffer 5-40 gave me the best OA and works with the least amount of hiccups so I've been using it exclusively for the past 2yrs.

Should add that the truck generally runs like ass after a fresh oil change no matter what oil is in it. Takes about 1000 miles before it wants to settle down.

powerSmokin · Jul 13, 2012

You checked for airation in the system? Kinda sounds like it.

TARM · Jul 13, 2012

Should add that the truck generally runs like ass after a fresh oil change no matter what oil is in it. Takes about 1000 miles before it wants to settle down.

That may be helpful in pointing to what the issue might be. What is effected by draining all the oil and filter removal?

caladash · Jul 14, 2012

Prior to me noticing this I was running rotella. The valvoline blue was on sale so I bought it. Once time permits I'm gonna clean the IPR and pull an injector or two to swap out the o-rings. Just to see what kind of condition they are in. This is on my excursion with almost 200k on the clock. Im really starting to think its injectors. If I idle for about 5 minutes, when I take off it smokes white for a few seconds then clears right up.

TARM · Jul 14, 2012

200k is about time for injectors to need to be gone thru from what I have learned so that is very possible. While you have the VCs off replace any glow plugs check the uvc harness connections. Would not be a bad idea to replace your valve springs as they are likely quite weak by now. Some like to wrench and pull apart their engines others have little time so for the latter it makes sense to get everything done you can so you are not going back to tearing it apart again.