This isn’t directly related to my Roamer refit, but it’s a contributor to the fact that I will not be getting the boat splashed this year.
A while back I wrote about how My Life Is An Old-School Country Western Song, one of the key factors of which is that a pickup truck must break down. A month or so after I got the transmission fixed in the new-to-me Nissan Frontier, which was part of the inspiration for that post, the missus reported that fuel economy in the truck was getting pretty bad. On our way down to the house one evening, the engine started sounding awful–like it was coming apart–and power dropped to almost nothing. I let off on the throttle until it sounded less grenade-like, at which point 20mph was top speed (35 going downhill), and when climbing hills it went down to 10mph. At idle, it sounded perfectly normal though it had a bit of a vibration. We eventually made it home, and I started looking into what might have gone wrong. All of the fluids checked out, but a compression test revealed strange results: 150psi on the three driver’s side cylinders, 200psi on the back passenger-side cylinder, but the center cylinder was not good at all.
The front passenger-side spark plug is inaccessible without pulling the intake manifold, but I already knew enough–the engine was in the process of dying. This truck with the low miles it’s got on it should still have high compression, so that one cylinder with 120psi was especially disturbing. The three on the driver’s side were consistent, but lower than they really should be with less than 100,000 miles on the truck.
Cue my theme song:
Truth be told, a light on the dash had been on since I bought the truck, and the codes it was tripping indicated the catalytic converters were shot. That was also a strange thing to happen with such low miles, but I wasn’t terribly worried…emissions inspection wasn’t due for another six months. When the transmission was being diagnosed, the shop also confirmed that the catalytic converters were shot. When I picked the truck up, the manager reiterated that the catalytic converters needed replacing. I downloaded the Torque OBDII code scanner app and a bluetooth sender while the tranny was being rebuilt, so I hooked that up to see what it had to say. Sure enough, the engine was still throwing cat codes but there were a bunch of additional ones, too. Figuring that the cats would have to come out anyway if I was replacing the engine, I went under the truck one weekend and got to work.
No doubt about it, the transmission shop had to remove at least the crossover pipe to get the transmission out.
You have to smack that pipe pretty hard to dent it. And according to the internet, one of the worst things for catalytic converters (after leaded gas) is hard blows.
It was around this time that I started wondering about the skills and practices of that transmission shop. Then I removed the catalytic converters.
The pictures above are of the driver’s side cat, which was completely destroyed. Chunks of the ceramic matrix and ceramic powder had broken off and shot down the exhaust pipe to the second catalytic converter, completely plugging it. On the passenger’s side, the matrix was starting to come apart but hadn’t completely undone itself yet. With the cats off the truck, it fired right up and though it was loud it didn’t sound like the engine was coming apart. I put new cats in, reset all the codes with the Torque app, and–lo and behold–the truck runs pretty well.
My theory is that while the cats were already gone before going to the tranny shop, the hammer blows on the exhaust pipe fractured the ceramic matrix. Vibrations from driving it for a month broke the matrix apart, and the more it self-destructed the finer the particles became. Eventually the rear cats got plugged with bits and pieces of the front cats’ ceramic matrix, and that was when the engine lost all power: the exhaust had nowhere to go.
Even after replacing the cats, the truck still had the same low compression. I read somewhere that these engines have no Exhaust Gas Recirculation system per se, instead they have quite a bit of valve overlap at certain throttle settings that draws exhaust back into the cylinders for another go-round. When the valves overlap and a catalytic converter has failed catastrophically, ceramic particles from the cats can be sucked back into the cylinders. I assumed that’s what happened here and was considering filing a claim against the transmission shop. But since the cats were already throwing codes before it went to the tranny shop, my case wasn’t as clear cut as I’d have liked. I kept driving the truck and just recently did another compression check on the five cylinders I can access. GOOD NEWS! Compression is 190~200psi on all cylinders!
My theory is that ceramic particles had gotten as far as the exhaust valves, holding them open just enough on certain cylinders to let compression leak past. Over a couple thousand miles, the particles got worn down or blown out, restoring compression to where it should be. The truck fixed itself! I’m hoping that good mojo will spill over onto my boat project, too!
With that drama out of the way, it’s time to get back on that Roamer refit. There’s another beautiful mahogany panel that needs to be installed in the V-berth.