I am having a mileage issue on my '93 3.0 V6. I have noticed a drop in mileage lately, about 2-4mpg depending on situation. I am trying to troubleshoot it w/ no electronic diagnostics. I have replaced plugs and cap and rotor lately. Truck runs fine, no seat of the pants differences. I am wondering if the O2 sensor could be going bad w/o any noticeable differences in performance. Any other ideas? If it is the sensor, other than dealer, where are they available? What is the actual brand? All my other cars have bosch sensors available through many retailers.Thanx in advance. andy
Could be change in gas formulation, could be gas cap seal is failing, could even be change in driving habits, could be all sorts of things that are minor and difficult to diagnose.
Did you check for stored ECU codes? That only requires a jumper and looking at the Check Engine light.
Poor quality plugs (Bosch) are a known problem with Toyota's stock ignition. A poor quality cap and/or rotor could lead to a slight decrease in efficiency. If you didn't use NGK or ND plugs, try installing those and see if your economy improves.
A failing O2 sensor will, 99% of the time, cause a code to be stored or most likely displayed.
Bosch may be the OEM for this item; there are SEVERAL aftermarket (Bosch, B/A, B/W) sensors that either come with a factory-acceptable harness, or can be easily adapted using the old harness.
good luck! GTr ps - on the economy thread: my 89 3VZ-E 4WD jumped from 17mpg to 21mpg due to: spring tuneup including greasing, change in gas formulation from winter to summer, and, perhaps the most obvious: removing the topper. While the weight (Brahma) is not signficant, the 'bump' that extends the roof height seems to have a dramatic effect on drag at highway speeds.
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