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Mileage down, not the usual suspects.

posted by  someone claiming to be Mr. Norm on  Thu Jul 21 15:03 CST 2011 [RELATED]

While the problem has been present for years, I am recently reminded after driving a 96 855 t5 instead of my 96 854 t5. The borrowed car consistently showed about 10% better fuel economy than my ride. This is magnified in strangeness as my car has the IPD chip and exhaust and the 855 had is stock. On my car, the mileage is better with the IPD ecu than the OEM, which I still have for comparison.

Each car was driven very gently in the granny mode to get a meaningful comparison. The 855 did have 15" wheels instead of the 16s on my car.

All the usual stuff on my car has been dealt with. Plugs, rotor, cap, wires, MAF, O2 sensors, coil, temp sensor, cleaned throttle body, you name it and it has been checked.

Any ideas on something obscure that could create this condition? I am thinking it could be something involved in the feedback to the ECU, which perhaps causes the motor to run rich. Perhaps the MAF wiring harness or the cable to the O2 sensor.

Any ideas? Thanks.







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    Mileage down, not the usual suspects.

    posted by  KlausC on  Thu Jul 21 19:34 CST 2011
    Author: [PROFILE] [EVERY POST] [THREADS] [BEST POSTS] RSS Feed     [IGNORE ALL POSTS]
    last visit: Fri Oct 24 10:15 CST 2014
    [RELATED]

    10% could be the normal difference in tire diameter and tread pattern. You didn't say what the mpg was in either car.

    Klaus
    --
    Always willing to listen, just not able to take direction.








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      Mileage down, not the usual suspects.

      posted by  someone claiming to be Mr. Norm on  Fri Jul 22 11:41 CST 2011 [RELATED]

      20.5 in the 855, 18.5 in the 854. Do you really think that this could simply be due to the different tires on the two cars?

      Thanks.








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        Mileage down, not the usual suspects.

        posted by  KlausC on  Fri Jul 22 13:55 CST 2011
        Author: [PROFILE] [EVERY POST] [THREADS] [BEST POSTS] RSS Feed     [IGNORE ALL POSTS]
        last visit: Fri Oct 24 10:15 CST 2014
        [RELATED]

        The more aggressive tread and width will have a negative impact. If the tires are new, less than 5000 miles on them, that also lowers the MPG.

        I know, the 854T should get 20-22mpg around the suburbs, but you need to check all of your vacuum line connections before you go nuts! My 1998 R is getting around 18 also, but that could be due to an O2 sensor with 188K on it. Or its very aggressive summer tires.

        Klaus
        --
        Always willing to listen, just not able to take direction.








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          Mileage down, not the usual suspects.

          posted by  someone claiming to be Mr. Norm on  Mon Jul 25 14:01 CST 2011 [RELATED]

          It's too late, I have been nuts for years.

          The entire motor was swiched to silicone hoses about two years ago just to avoid the possibility of vaccum leaks.

          Any other ideas?

          Thanks again.







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