Fun one

[7.3 rocket]

213k mile late 99 7.3 auto

Truck developed a slight but noticeable miss on my way home one night.

When I started the truck next morning it was like it was 0* out (it was in the 70s) long crank time and romping upon startup. Drove it to where I keep my trailer loaded it up and brought it to a friend's shop. Truck would repeatedly try to die on me and did die a few times and needed to be cranked a while to re-start.

Changed all fuel filters (in-tank filter eliminated and filter put on frame)

Figuring we might have had a bad injector o ring or hung poppet we put in a set of known good stock injectors and new motorcraft o rings.

Same problem.

Checked fuel pressure via gauge tapped into filter cap. Holding 60psi from the second they key turned on to key off.

ICP sensor, IPR, and CPS changed with new OEM parts. No change

Tried known good PCM and IDM and ohmed wiring between IDM and injectors. No change and wires ohmed out fine.

Scantool shows that the truck is losing ICP until it finally dies.

Going to try an HPOP next as I can acquire one for free from a friend for testing purposes.

Hoping someone might have an idea of what else it could be. The oil press dash gauge is reading normally and when the IPR was pulled plenty of oil puked out so I don't see how it could be the LPOP.

Anyone got any ideas for me? I'm about out of ideas.

 

[ToMang07]

You put the scanner on it to read ICP/Voltage?

 

[7.3 rocket]

Snap on scan tool yes. Cct yielded no significant result all injectors buzz no consistent code

 

[OBS-Addiction97]

How are the uvch's???

 

[7.3 rocket]

How are the uvch's???

They are original to the best of my knowledge but they pass a continuity test and a visual check.

All injectors buzzed when the buzz test was performed.

Truck will idle for ~30 seconds it may have a light skip tough to tell. If you then bring the RPMs up it starts missing and you can watch the ICP drop off until the engine dies.

 

[OBS-Addiction97]

They are original to the best of my knowledge but they pass a continuity test and a visual check.

All injectors buzzed when the buzz test was performed.

Truck will idle for ~30 seconds it may have a light skip tough to tell. If you then bring the RPMs up it starts missing and you can watch the ICP drop off until the engine dies.

I might change them for peace of mind if it was me.

 

[7.3 rocket]

I might change them for peace of mind if it was me.

Ordinarily I would but I'm waiting for a lineman's apprenticeship to start in 2 months and I'm having a really tough time finding work until then. (nobody wants to hire someone they know is going to be gone in 2 months) And I have to drive 40 mins each way to pre-employment training on weekends plus buy books and tools before I start getting paid.

So usually 80 bucks for new harnesses would be a no-brainer but 80 bucks will get me to and from the hall for a weekend. If I could guarantee that it'd fix the issue I'd do it but I can't afford to throw parts at it right now. They will be changed eventually. For now my 6.0 is getting me where I need to be.

 

[7.3 rocket]

Ended up being the HPOP for anyone who ends up on this later via a search.

 

[Derek@Vision Diesel]

They are original to the best of my knowledge but they pass a continuity test and a visual check.

All injectors buzzed when the buzz test was performed.

Truck will idle for ~30 seconds it may have a light skip tough to tell. If you then bring the RPMs up it starts missing and you can watch the ICP drop off until the engine dies.

Low pressure oil is good?