My truck has been missing or stumbling on occasion. Recently got a code 1280 with a CEL. This morning went to work, truck ran fine and then went to extremely rough idle and could barely get over 15 mph. CEL on and code 1280. Disconnected the ICP censor with no change in how the truck ran.

Ideas on where to start looking for a fix? HPOP out? Any help appreciated.

 

Here is the code description for the code you're seeing:
P1280 ICP Circuit Out of Range Low
My WAG would be IPR issues. The HPOP doesn't usually just quit. You might try replacing the IPR O-rings first. There wasn't oil inside the electrical connector for the ICP was there?

It could also be a badly blown injector o-ring, but you would have a black oil filter if that were the case.

 

Did you unplug the ICP sensor before you checked for codes? Unplugging the ICP will set a P1280.

If the code came from you unplugging it, then you need to check fuel pressure.

 

I got the P1280 code before unplugging the ICP. I have 250,000 miles on the truck, original injectors, ICP, IPR.

The truck has been stumbling or missing on occasion for the last several months. Only a couple of times like bad gas or clogged fuel filter. I did change the fuel filter a couple of months ago around that time the stumbling started to occur.

I got a CEL a week ago after hauling my 5th wheel camper home from Denver while parking it in the driveway. The truck would be idling and just shut down or pause for a second while unhooking the trailer. Truck ran great hauling the load over the passes and in rush hour Denver traffic, never a miss. The CEL code was the P1280 again.

Several months ago I got a P1280 code and there was a little oil in the ICP sensor when I unplugged it. I blew it out with compressed air and the code went away. No oil in it this morning and I was wondering if the ICP sensor was going bad. Disconnecting it did not change how rough the truck was running so I am guessing it is something else.

I will go and check the fuel pressure right now - if it will start and run smoothly and post what I find. Thanks again for any ideas on where to start looking for a solution.

 

Truck started up like normal. Sounded great again. Fuel filter is clean, no black staining and full. Fuel pressure at idle after starting it and without revving the motor is 54 psi.

Disconnected the ICP and the idle changed slightly with the disconnect but still smooth on PCM presets. CEL light lit up of course after disconnect. Cleared that.

Where next? New ICP sensor? Take apart the IPR? Need to get the bugs worked out as I don't want to break down deep in the mountains or on a road trip with the 5th wheel.

 

If it will stay at idle, I'd start wiggling the harness to the ICP and IPR and see if you can locate a short in the wiring. (truck stalls or idle changes as you move wiring around)

 

Doesn't appear to be any shorts. No change while wiggling the wiring harness to sensors.

 

Since I am in there fiddling with things anyway, I went ahead and shimmed my FPR. Now I am getting 74 psi at idle.

Took the truck out for a test and it ran great - like usual. The throttle seemed even more responsive with the FPR shimmed.

The only thing I can think of is that the ICP is beginning to fail or is failing intermittently? What is the story behind finding oil in the connector for the ICP? That did occur in the past but hasn't returned since I cleaned it out a few months ago. A new ICP is around $150. Anyone had these engine "stumbling" or "missing" symptoms and CEL P1280 prior to ICP sensor failure?

 

Maybe when your ICP is hot it will leak indicating the seal inside is getting old. Its probably just a matter of time before its no good. I bought one on ebay for cheaper then $150 but that was several years ago. I also pull a 5er and I've replaced all my sensors because I don't like being starnded. Keep the old ones as spares.

 

If it ever had oil i would replace it.only a matter of time till it craps out....if you pull the ipr you can look at the oringsi onit also.but would think replace theit icp and retest.-i think clay has oe for less than 150.

 

If you're going to pull the IPR just plan to replace the o-rings. Riffraff and or Bob (Dieselorings.com) have them for cheap. There's a good possibility that the o-rings could be your issue anyway, and since they're cheap.... I would just do it.

 

Thanks for the input. I will get a new ICP and replace the old one keeping it for a spare. I already carry spare CPS and GPRs. I agree, if I am going to pull the IPR I might as well replace the o-rings since I have it apart so I will get a set coming. Thanks for the help. I will post the results.