When I come to a stop sign or rev the engine, when the RPM's fall they fall really low then mosttimes they pick back up and it idles ok. Once in a while it will fall low enough it will die and need to restart it. Seems to do it once it warms up alittle. It also sometimes seems to have a rough running at idle sometimes but runs fine down the road. I'm thinking IPR or ICP. Should I unplug the ICP and see if it makes a difference?

 

I'm having the same problem. I have replaced the ICP, IPR, CPS and have new injectors and hpop. I'm down to blaming it on the chip and sent it in for a reburn. I'll post back if this works.

 

I do have a chip so that's possible. It's a 4 position aiken chip with TW Tunes on it. Think I'll try unpluggin the ICP first then maybe pull the chip.

 

My RPM fluctuation was not as extreme as yours...like it never died...it was my alternator getting weak....like 13.3 V measured from the back of the Alt. at Idle...Installed a new Alt. putting out 14.5 V at idle......problem went away...

 

Unplugged the ICP sensor and no help. I then measured the alternator output and I was only getting 13.0 volts at idle. i'm going to swap the alternator out with my uncle's and see if it fixes it.

 

Won't be able to swap the alternators till monday at the earliest so I thought i'd take the chip out and put one in that I got for my uncles. I took it for a drive and the problem is still there. So in my case the chip is not the problem.

 

fuel pressure sensor. i had the same problem it died when i came to a stop. replaced the sensor and fixed the problem.

 

I deleted the fuel bowl and only have the regulator up there with no sensors of any kind on it. Pretty sure these trucks don't have a pressure sensor. They have a water in fuel, filter restriction, fuel heater and that's it on the fuel side.

 

^^^^ This. Fuel system is completely mechanical. No fuel pressure sensor. Even the sensors on the bowl are strictly for the dash lights, and couldn't possibly affect engine performance.

 

sorry i dont know the exact name its be awhile but it was something with the fuel that when the RPMs drop the computer thought there was not enough fuel pressure and cut the engine off.

 

Maybe your thinkin of the ICP (Injection control pressure) sensor that reads high pressure oil to the injectors. I unplugged it and still had the same problem. I have a spare cps i guess maybe I should throw that in for poops and giggles. Can't hurt=) Then will be an alternator swap and then my spare IPR if that don't fix it.

 

Still no such thing. The PCM monitors and regulates HP oil pressure, not fuel pressure. Hmm, it is possible that old/weak oil could cause something like this.

 

Not able to swap alternators but a new symtom occured. I started it a few times and instead of dropping low it started to ROMP hard. Like from 450 rpms to 750 rpms and would smooth out after revving the engine. It did that a couple of times today. I've searched alittle and seems that the gear selector switch can cause romping. Could this be my issue? Any other thoughts?

someone else's video but exactly what it was doing. After he revs it you can see rpms drop down to 500 rpms and come back up to normal idle. That's what mine is doing, but a little more severe.

http://s203.photobucket.com/user/agw...d359a.mp4.html

 

Finally got AE on it and ran a cylinder contribution test on it and kept getting a P0272 cylinder 4 balance/contribution fault. Pulled all the valve cover connectors and this is what the pass nearest firewall looked like.

Gasket looks worse but the under valve cover harness is fine. This is the second time this side has had problems. I put in new glowplugs 2 years ago but i'll ohm them in a little. I'm thinking of putting SD valve cover gaskets on cause of the bigger wire for the glowplugs. Any Opinions?

 

That's part of the reason I went with them. Another reason is buying them from riffraff, they are quite a bit cheaper than the obs ones. If you put them on, do the 50 cent mod. Look it up in the SD forum if you don't know what it is, it's easy and quick to do, and costs 2 quarters.