We're back a little earlier than intended. There were a couple of things which contributed to this.
I had an injection actuation pressure code & CEL prior to leaving which I thought I had addressed. The truck ran flawlessly and felt great all the way down and into the backcountry. We had our day at the Wave and things went great. While moving truly into the wilds, transiting through sand while climbing a consistent grade and on a road where there was no turning around, the code/CEL came back. This time, it also went into limp mode (or so it felt- I think I had 6 hp). Before deciding to start this leg, I consciously thought about how things were running and that it went so smoothly getting to where we were- so we went... and now we had to get out! Fortnately, we were able to negotiate the entirety of the terrain (sand, rock obstacle, gradient) to make it back out to the main dirt road (House Rock Valley Rd).
Since it was running, I decided that we were getting all the way out to at least Rt 89, if it allowed. On House Rock Rd, it was possible to get it up in the gears and start making some progress, so it didn't take us long to get out to 89. Since we were to 89, and still running, I decided it'd be ideal to get back to Kanab, so off we went.
In the surprise of surprises, as I turned onto 89 and accelerated away from the junction, limp mode switched off and I suddenly had all the power back and the CEL was out. This was a relief, but I was pretty sure it didn't just fix itself. We made it back uneventfully to Kanab and I got out the diagnostic gear.
CAT ET was showing that the actual injection actuation pressure was WAY high compared to the desired injection actuation pressure. They should ideally be identical and only fluctuate minimally. After a bit of internet scrubbing and checking in with Rick, a pretty basic plan was for an oil change and see what happens. I had a recommendation for Color Country Diesel in Cedar City and went there for Mon morning. I chatted with their resident CAT guru and he didn't have a clear direction for resolution. I could be the injection actuation pressure control valve, which literally is what controls the parameter that is running erratically. Based on it starting when warm, he didn't think it was injector o-rings, as if they are the issue, they have a hard time holding pressure once the oil is warmed up and less viscous. The next options were HEUI pump and injector replacements... Not something I wanted to do on the road, so time for an oil change to 10w-30 to see what'd happen.
Getting out the computer again, the called pressure and the actual pressure were matching everywhere in the rev range except at idle. I did some laps around the block and it was consistent. Repeating the diagnostic tests, it was still consistent- couldn't get to the 870psi setting (about 1000psi actual min), but anything beyond that, it was matching almost identically (+/-10psi). At this point, I was comfortable enough to get back on the highway and head home.
We got north of SLC that evening, and wrapped up the trip Tues night back to PDX.
Interesting observations:
If you're worried about tire balance, drive your rig. I was told by a local motorpool guy that these tires flat spot easily just from sitting a little bit. I can tell you from firsthand experience after ~1200 miles each way, they will smooth out if you drive them. There are times when the CTIS hardware synchs up (I think) and there is definitely a shimmy to things, but there are also times when I looked down and was surprised by what the speedo said- couple of times even hitting 80. Seriously.
I can honestly say that I struggled at times to keep it
under 70. I found that at 65, it runs well, and just a little more makes it a little faster... But I think that 65 is a sweet spot on my rig. We were under some time pressure on the way down and I ran it pretty fast to get there- not really caring about economy and just letting it run. Fully loaded, full water, single spare, a week's worth of food and supplies, all sorts of gear, wifey and dog... I got mid-6's for MPG. I would guess that's somewhere around 27k but I didn't weigh it.
On the way home, no rush to be anywhere, still just about the same weight, etc... I specifically burned a tank trying to stay at 65 MPH. This one mathed out to 8.15 MPG. For what it is and what it's doing, I am pretty OK with that.
I was nervous about how it'd do up hills, especially with 80 MPH speed limits and some of the passes we'd head over. We did just fine and typically better than the average big rigs out there. Most times, I was able to keep it above at least 50 MPH, but if I couldn't, there was plenty of other slow truck traffic out there to keep the rockets out in the passing lane.
Finally spending some time in the rig on dirt roads was amazing. We aired down to ~35 psi for House Rock Valley Rd and it was like the washboard stuff didn't exist. It
did, because I could see us driving over it. Compared to how our van did, this rig just floated over it magically. It was truly fantastic.
Last major revelation was about how it did in the sand. In short, it was amazing. It was ripping through it. I aired down to 28-30 psi and it seemed to just eat it up, even in limp mode. These are highly impressive machines.
All in all, it was a successful trip despite heading home early. We were lucky to get a permit for the Wave and super excited to get in to it at this time of year. The BLM allows 64 people in per day, and we were out there early enough that we had it to ourselves for our own photo shoot session (30-40 min?). We sat down for a bite of food and it suddenly seemed like rush hour with people coming through every 5 min. We went on a hike around the other features and when we came back, we once again had it to ourselves. Another friend has a permit for a day in May, so we're going back with them. Will be interesting to see how it is during the more amenable weather months. Need to get cracking on resolving the pressure issue!
I will shortly start another thread over in the LMTV forum for resolving the injection actuation pressure issue, just to keep the technical discussion in that forum where people will most likely look for it if they have similar issues. If you have any camper or over-the-road questions, fire away!
Chris
