There is an interesting one at my shop. We have a 1MZ-FE in a Highlander (an
01, I think) that was just rebuilt. I don't know what the circumstances of the build were, but I know the pistons were out. Now, apparently it started up fine and idles/runs without any obvious problem, but the data list shows that it is running super super super lean. Here are some figures from the list that I remember (figs. are @ idle)
MAF:1.86 gm/sec Coolant temp: 186F AFS bank1: 3.70 AFS bank2: 3.86 Short fuel trim #1:19.4% Long fuel trim #1: 52.4% (wow!) Short fuel trim #2: 19.4% Long fuel trim #2: 52.4% (holy crap!) Total FT#1: 1.52 Total FT#2: 1.52
02s: .1v Cylinder #1 misfire: 0% ""2: 0% ""3: 0% ""4: 0% ""5: 0% ""6: 0%
The parenthetical superlatives were added by me, by the way. Someone switched out the MAF sensor with a new unit first just to see, pulled the EFI fuse, and the numbers climbed right back into the clouds in a couple of minutes. There are no audible vacuum or exhaust leaks, and we did a propane test around the intake manifold to verify. Vacuum hoses have been triple-checked for cracks and routing, with no problem found. All injectors are cycling, and plugs are new. No signs of a misfire exist. I did open the airbox, though, while it was running, and I heard a rythmical pumping leading into the intake. Sounds similar to uneven engine pumping that comes with one or more inoperative cylinders. A manifold vacuum reading also shows a slightly fluctuating reading between 19 and 23 in/hg. Hmmm. We also did the AF active test (switching between -12.5% and +25% trim). During the lean cylce, both AF sensors showed 4.00v, yet the rich cycle only brought them down to 3.3v (which is where they should be in the first place). So anyway, who the hell knows. The thing is desperately trying to give itself more fuel, but it just ain't clicking like it should. Any takers? MDT? Tegger?
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