1991 Lexus LS 400


August, 25, 2008 AT 9:10 PM

Computer problem
1991 Lexus LS 400 V8 Two Wheel Drive Automatic 113040 miles


I have owned four 1990 LS 400's in the last ten years and currently own two 1991 LS 400's. I always get 22 MPG on all of these cars. The one I just got and drive is only getting 10 mile per gallon. The car has been checked out on two electronic machines by two different reputable repair shops and no problems were found. One mechanic made a comment that the 0 2 Sensors were changing slowly. Can a faulty 0 2 sensor cause this problem? There are three, which do I replace? Any other answers to my low gas mileage?

1 Answer



August, 26, 2008 AT 7:04 AM

O2 sensors are a critical part to air/fuel ratio. You should be seeing black smoke out the exhaust.

I would also do a backpressure test done on the convertor. A rich mixture will overheat the convertor and cause a partial or complete blockage.

If the convertor is blocked you will need to find the cause, most likely the O2 sensors, I would replace them all.

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