I got the Rodeo back.

- They pulled the intake, looking for carbon.
- The pull the plugs, looking for carbon.
- They checked for loose bolts on the cam gear. Thought that was odd, given the known cam issue. Though, they didn't mention that a few have snapped.
- They recommend haveing it decarbonized regularly, and using an injector cleaner. When I told them I did it myself, last month, and spent $40 on fuel aditives, they didn't respond.

Next, I call Isuzu, again. I will not chip away carbon at EVERY oil change. I'm told no one else does... Why should I??

I don't know about the DI engine but on a 3.5 Trooper you have to clean the EGR and the return tube to try and stop the oil burning cycle. In fact a plugged EGR is really the main culprit in high operating temperatures/carbon formation. Again cleaners in the fuel only attack part of the problem as does cleaning the intake. Cleaning the PCV also is important. I know you mentioned these early on but I don't see that you did clean them.

Too high an octane fuel can facilitate carbon buildup. What octane fuel are you using?

Lastly bad O2 sensor readings can lead to too lean conditions which raises combustion temperatures and can lead to carbon formation. Granted the computer is usually very good about detecting a bad O2 sensor. However you seem to be looking for any options. It might be worth a new upstream sensor on bank 2 (the side with the original code). Worst case is you keep the old sensor as a "trail spare". Again not a likely cure but at this point it might be a last resort type step.

The good news is that the design of the EGR circuit is different. It's not going to clog like the other 3.5l, and other types. Still, I'm watching it.

We burn Chevron regular... The lowest they have.

O2 sensors are funny things, it's true. In this case, I'm not suspecting a sensor failure.

It's frustrating. For the most part, all is well, but no one did anything. HUMmmmmmmmm. I don't believe it's over. In a month, we'll be talking about carbon again, even though Isuzu, and the dealer say I'm doing everything right.