Sudden Drop in Gas Mileage

Discussion in 'General Motoring' started by Doug Burgess, Oct 2, 2003.

  1. Doug Burgess

    Doug Burgess Guest

    Since I purchase my '96 SL2 used with 29K miles, I've gotten a consistant 26
    MPG in town (auto). It has suddenly dropped to 21 MPG. As far as I can tell,
    the performance is the same.

    Any ideas?

    Doug in Fremont CA
    Doug Burgess, Oct 2, 2003
  2. Doug Burgess

    Ed Guest

    How many miles does it have now? If over 50K you should check your 02
    sensors. If they are sluggish but not quite failing enough to set a code
    you will lose efficiency.
    Ed, Oct 2, 2003
  3. Doug Burgess

    Ratbert Guest

    How do you check O2 Sensors? I have a 98, 94000 mi, and have recently
    experienced a similar drop.
    Ratbert, Oct 3, 2003
  4. Doug Burgess

    Doug Burgess Guest

    I've got 40K miles on the car.

    Doug Burgess, Oct 3, 2003
  5. Doug Burgess

    Kirk Kohnen Guest

    Check the coolant temperature sensor.

    They fail often on Saturns.

    One mode of failure is they think the engine is cold and they run it rich.
    Kirk Kohnen, Oct 3, 2003
  6. Doug Burgess

    BANDIT2941 Guest

    Check the coolant temperature sensor.
    You would also notice a high idle if this is the case. Also, the fan would
    never come on unless you put the A/C on.
    BANDIT2941, Oct 3, 2003
  7. Doug Burgess

    Ed Guest

    You need an o-scope to properly check 02 sensors. Best bet is to take the
    car to a mechanic/dealer and have them hook up their scantool and perform
    the diagnosis for you, one or both of them may be sluggish.

    Alternatively, 02 sensors are relatively cheap, buy them at your favorite
    parts store and replace them one at a time or all at once. The upstream
    (first in line) sensor is the one that tells your computer to lean or richen
    the air fuel mixture, the downstream one monitors catalytic converter

    All this is of course assuming that your SES lite is not on and no DTCs are

    Ed, Oct 4, 2003
  8. How does one test this little monster, as I have all the symptoms listed above
    (or, rather, my '95 SW does).
    William Hughes, Oct 4, 2003
  9. Doug Burgess

    BANDIT2941 Guest

    You can test its resistance. I BELIEVE there is a table of accepted values for
    each temp range in the Haynes manual. But its probably easier to just change it
    if you exhibit the symptoms - it was only about $11 at NAPA to replace mine.
    Regardless, its cheap insurance since it is a very common failure on Saturns.
    BANDIT2941, Oct 4, 2003
  10. Thanks. If anybody wants me on Sunday, I'll be out in the garage.
    William Hughes, Oct 4, 2003
  11. Doug Burgess

    BANDIT2941 Guest

    You can test its resistance. I BELIEVE there is a table of accepted values
    If you're looking to get away, you may want to find more stuff to do, since
    replacing the CTS shouldn't take you very long :) :)
    BANDIT2941, Oct 4, 2003
  12. Bah. Had a list of things to do - all those little five and ten-minute jobs that
    pile up; was going to get 'em all done. Unfortunately, something's come up and
    I'm going to be busy tomorrow. Guess I'll do it next week.
    William Hughes, Oct 5, 2003
  13. I had the same problem on a 94 SL2.

    After many times to the dealer I found out my oil level was not high
    enough. Topped it off and that was that. Could not believe it was
    that simple.

    Since then I always check the level. Check the obvious.

    I did have that sensor replaced as well as it was failing but did not
    fix my mileage.
    Scott W. Petersen, Jul 20, 2004
  14. Doug Burgess

    D. Gignac Guest

    same problem on a 93 SL1, it was MAP sensor
    D. Gignac, Jul 20, 2004
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