Mostly Looking for a sanity check that nothings wrong or direction on where to test next!
2000 F250 Lariat Auto 7.3 4x4 342,000miles

Lately ive noticed once the truck is warm, sitting at a stop light or if i let it idle at my destination there seems to be a noticeable "stumble" in the idle of the vehicle. It drives normally, power seems to be normal when driving. I am due for a couple road trips over the holidays and want to rule out any major issues that would leave me stranded. I previously had an issue with a bad CPS and my truck dying in HWY 98 traffic which was super not cool if youve ever experienced that and i would like to avoid that as well.

The diagnostics ive done so far have lead me to rule out the ICP, IPR and UVCH. Ive unplugged the ICP while idling, no change to the idle. Ive taken the attached forescan data with the IPR % only falling below 9-10% after a letoff of the accelerator for a very short time. Otherwise the data seems normal for an amateur like me. Recently i did the "50C Mod" and re torqued the injectors and rockers, rough idle was present before that so i dont THINK i made it worse while monkeying around in there. The truck also likes to do a long crank when hot BUT ONLY randomly, not always when its hot which also stumps me. The valley is completely dry, only signs of leaking oil are a mystery leak on the front of the engine, (see pictures) which i think may be a shoddy RTV job on the HPOP bolt cover. The oil drain plug has a slight weep and the oil dipstick tube where my repair was unsuccessful. The truck is definitely burning oil i was about 2 QTs low after about 3000 miles, maybe its an oil consumption issue? Theres no smoke on startup or when normal driving but a good amount of blue/black when i get on it and especially at WOT. The fuel in the fuel bowl is clear and clean diesel, the coolant doesnt separate into layers indicating diesel and my pH reading on the test strip had it at 1600 PPM or 1.6 on the SCA units per gallon.

I conducted a engine cold and hot buzz test with 0 errors and all sounding similar.

Engine contribution test identifies and error on cyclinder #8, which is unhelpful as generally thats seen as a "ghost code" or at least thats what my research tells me. Other codes it currently has are:
PCM
P0603 Power interruption on KAPWR (recently disconnected batts for mod see below)
GEM
B1352 Ignition key in circuit fault (annoyingly dings at me even when key not in)
P1876 Transfer Case 2-Wheel drive solenoid
P1812 Four Wheel drive mode select circuit failure
P1832 Transmission Transfer Case 4WD Solenoid Failure

Recent Mods or Repairs within last year
BD Diesel Bellowed Up Pipes
Hutch/Harpoon- Driven Diesel Kit with inline filter, deleted in tank filters, truck runs below 1/4 tank
50 C mod
PCC Battery Cables
Brand New Batteries (X2 Power 950 CCA AGM)
New Trans Filter and Fluid, no flush
6637 Filter
Re Seal Fuel Bowl
New Hard Fuel Lines on block
re seal oil cooler with new o rings and gaskets
New ICP w/ Pigtail
New IPR pigtail
new “Dark Blue” motorcraft CPS

Again, if i am overthinking this and it could just be some dirty fuel or these old trucks idle rough thats fine. Mostly want to rule out failing HPOP, IPR or LPOP, or something else that if it breaks on a road trip it would be a huge bummer. Also dont want to fire up the parts cannon unless i have a nice CAT 1 grid.

 

Pics mentioned above.

 

I had been fighting something similar for the last couple of months. Idle, when hot, would be a touch unstable and it would crank a bit longer when hot. Nothing crazy but I noticed it. I rebuilt the IPR with no real change. After watching the truck for a bit I decided to take a chance and get a new IPR as my current one was atleast 20 years old. The new IPR resolved all of the annoying little issues. Just something to think about as these trucks age.

 

kinda looks like an oil cooler seal blown out on the front side, or the front gasket is bad...with all that oil on the lower radiator hose.
I just put new seals on mine due to a nasty leak like that....and the PO had forgotten to put the gasket on the front.....it was just spraying out the whole time the engine was running.

 

Good point about an aging IPR might be worth just getting a new one before they become even more prohibitively expensive. Valid point about the cooler I forgot to add that I had re sealed it with new o rings and gaskets, maybe I didn’t do it correctly! Al thought that oil leak has been there in this same fashion before I did the cooler

 

Those files look good to me. A little ICP/RPM wavering at idle, but hard to tell if it's significant. I'm looking at areas where you just come to a stop to see if it hiccups there, but I don't see it. Your observations are best. If it runs similar with ICP disconnected, including a short drive with a few stops to check idle, then IPR valve is the next most likely cause of idle roughness or stumble.

Do you know what your fuel pressure is at idle and under load?

What tunes are you running when you captured this data?

 

Interesting comment. I too have noticed the occasional odd idle, usually after climbing a relatively steep hill near the gym. When I park it an idle it, there seems to be a little hitch in it I can feel. Since all Excursions are 50 state emissions, it runs the cylinder contribution test at idle at operating temp and it will throw the "ghost code" for #8 miss. Tempting to take the same chance as you.

 

I don’t have a fuel pressure gauge to read those metrics unfortunately.

No tunes loaded to my knowledge. It’s only been in my ownership for the past year and half and PO said there was never a tune on it. Although with some of the things I’ve uncovered I don’t know if he was completely honest so maybe I’ll pull the PCM when I have a chance and see if there’s anything in there.

Does some of the data indicate a tune?

 

In your Evening Drive file, I see what looks like a WOT acceleration. APP is almost 75% which is near wide open for these trucks. Boost is 16.6PSI max, good for a stock turbo. I see fuel pulsewidth go up to 4ms, and ICP is only 2300psi, with IPR% climbing. I think if you stayed in the pedal, it would keep climbing, like it's not getting the ICP it wants for a given MFDES, and takes PW instead. It made me think you had a tune at first, but if it's really a stock tune, I'm wondering if this points to an HPOP wearing out or tired injectors. You have normal ICP and IPR% at idle - no leaks there.

I put your chart next to mine, when I was running stock injectors, stock tune and stock HPOP, to compare. No "stinky spike" on ICP when you let off the pedal, like I would normally see with a 4ms pw and ICP not keeping up.




Can you post a drive with a couple of WOT runs, ideally up a hill so it takes longer to get to speed, and we can see how it behaves.

None of this is a large concern, if you are not asking maximum power from the rig, but it may point to the need to refresh some parts down the road.

 

Interesting! I haven’t heard of the stinky spike. I’ll keep my eye out for the next live data. Worn HPOP and tired injectors would make a lot of sense given the miles and that I believe they are both original.

I’ll try and get some more WOT runs, hills are hard to come by in Florida and the highway patrol are sticklers but good thing I’m in a 7.3 and WOT won’t get me in too much trouble with the law 😂. Not planning on asking a lot of it as far as performance goes but I do have plans to take it up into the Colorado mountains later in the winter where the altitude will probably stress it.

would the oil leak potentially point to a failing LPOP? Or Front cover/front main seal? Could a tired LPOP also cause a rough idle?

 

I don't think so. If the HPOP reservoir got low due to an underperforming LPOP, you'd have idle and running issues. but if the reservoir is nearly full when you check it, likely the LPOP is fine.

I've been meaning to test my LPOP oil pressure - I have a fitting coming that should allow a gauge to be mounted where the fill plug is on the reservoir, to get a cold idle and hot idle reading as a benchmark. I'm going to change my LPOP just because, since the crankshaft oil seal is leaking a bit.

 

Here’s two from today I’ll try and get a few more over the next few days

 

Just a thought, but rebuilding the IPR does not change the IPR solenoid. That's the **** that controls it's function. The main failure symptom is it fails when warm. Only available with new IPR and as you might expect we only recommend OEM from reputable vendor like Riff Raff or Diesel O Rings.

I have not viewed your new csv files fwiw.

You need to get this sorted before Colorado. Altitude is an issue but the steep grades are the main issue, especially if towing. Build for EGTs and trans temps. 6.0 transmission cooler top recommendation.

Got tunes on the truck? EGT/trans gauge?

 

Yep! If I decide to replace it will be a genuine motorcraft from either of those vendors or CNC fab!

lucky nothing being towed this trip, I do plan to get around to the 6.0 cooler one of these days but I’m trailer less at this moment so it’s not a huge priority. Definitely want to make sure this thing is running reliably before I get it at 9,000 feet in December though!

 

Looking at those 2 WOT files, it does look like ICP is lower than normal, but the PCM is adding PW, and the rig is performing well. You could change out the IPR and see if your rough idle smooths out. Checking for fuel aeration is another possible cause - usually from the fuel line connections between the tank and frame rail pump ( the suck side).

I measured your 20-60mph time on WOT 1, and it's 7.6 seconds, good for an empty truck on a stock tune. What is your truck's cab and bed size? Wanted to get an idea of the weight.