I noticed this a.m. while at a red light that my tack would jump up a notch every now and then. I couldn't really tell if it did this while the a/c compressor was cycling or not. I was thinking maybe my ICP sensor is bad due to little oil in the connection, but haven't had any problems with the way the truck runs. Any ideas what would cause the truck to idle smooth and once in a while rpm's to jump up?

 

Depends on how far it's moving. There can be some slight variations at idle due to different factors, but if it's getting jumpy and you start to see the tach bouncing around at times, I would probably attribute that to either a bad ICP or an IPR.

Unplug the ICP sensor and see if it idles smoothly. If it does, you've found the problem. If not, then it might be the IPR. To check the IPR, hook up AE and start tracking pressure and duty cycle. If duty cycle and pressure are bouncing around quite a bit, then the IPR is toast. Pressure can fluctuate a little, but duty cycle at idle shouldn't.

 

Thanks for the info Curtis.

I've heard of possibly rebuilding the IPR, is this possible? If so how would you go about it?

 

Found this info threw searching. Looks pretty good.

http://cw-diesel.com/LuxSite/IPRInfo.htm

 

Glenn, my truck used to twitch the tach needle just ever so slightly at idle, and when the needle moved the sound of the motor changed just a bit too. Since installing my Riffraff HPX it got better, but is still there. I think you might have an injector O-ring issue, that is what folks have told me is my likely problem. Just some more food for thought.

 

Good point Chase. Is it easy to replace injector o-rings?

 

Gotta yard the injectors out, suck fuel/oil out of cylinders... I've never done it but as I understand it's not too bad a job.

 

Are there any other sings of injector o-ring problems...maybe oil lose or coolant or something?

 

Typically harder starts and extended cranking. Also in some cases, HPOP oil bleed-down when sitting overnight.

 

Hmmm. My truck runs perfect (knock on wood), actually starts faster after my CCK was installed. Its never been hard to start.