TOPIC: 1998 Isuzu Rodeo - 2,200 cc

I'm very late in posting this update, but wanted to say that when the owner got back to me about mileage, he said there wasn't any improvement. He was still very happy since he'd got the 35-45% power gain and when I suggested a visit to see if we could figure out the mileage issue, he mentioned he'd already sold the vehicle (he sells vehicles for a living), so I won't be able to do anything more.

I know better, but didn't check for vacuum leaks or cap the PCV after the mod since he was so happy with the increased power - so those could have been the reasons he didn't see mileage gains.

Having now read about rerouting the idle air, I'm wondering if that could have been an issue. It entered in front of and pretty close to the middle of the groove. I also only took a photo of the TB before, and not after (more egg on my face). But.. based on the attached photo of the TB, do any of you have opinions about whether I should have rerouted the idle air?

Fortunately, as I mentioned, he was happy in spite of no improvements in the mileage and we're now planning on doing a 2001 Toyota Yaris he has.

There is a "sleeper" in the woods, Jonathan. More and more we are finding that a tired O2 sensor will cause the ECU to refuse to adapt.

There is no way around it in cases like this but to replace the thing. If you've done a thorough job of ensuring the integrity of the intake system, and cleared the ECU and it STILL doesn't show increases (or changes!) then that is probably the culprit.

THANK YOU TO AARON AND SCOTT!!!!

The last thing to check would be the head gasket. Many times, they will develop slight leaks and there is no cure but to replace the head gasket(s). That's really good here in Gadgetman Land because you will KNOW KNOW KNOW that everything is hunky dory!