Fuel Economy Poor

kam3radkam3rad Band Wagon
in Engine & Drivetrain
My 89 Wagon 4WD only gets in the low 20's MPG. Where should I start looking to see what the problem is? I just changed engine oil after 6 months (I know I waited too long) and that raised the mileage from 19 MPG (put in Kendall semi-synth). Could it be the oxygen sensor? I kind of doubt it since it just passed inspection but just trying to think of ideas.

Thanks in advance for any ideas!

Comments

  • shenrieshenrie Council Member
    Things that need replaced at least once a year. Like cap and rotor, spark plugs, maybe even wires if they have a lot of resistance. Definatly a K&N drop in filter or at the least a new paper filter. Use only NGk stock replacements for the plugs too.

    If you dont like future problems, only use Honda parts for anything inside the distrubitor. Thats where these cars have the majority of thier problems.

    Try those things. I just replced all that stuff for a friend of mine with a 93 Accord (hes very mechanicaly un-inclined) and he told me it got him another 7-8 mpg in town. HTH.
  • kam3radkam3rad Band Wagon
    Thanks shenrie. I last installed all those parts four years ago using NGK plugs and wires, YEC dist & rotor so I guess it is time to replace them. I ordered them plus a K&N drop in performance filter as you suggested. I'll wait on the wires - the NGKs I have look and feel like new. We'll see. I'll update this thread with my results.
  • kam3radkam3rad Band Wagon
    After changing the cap, rotor and plugs and a putting k&n filter in I am getting 21.6 MPG, that's about 2 MPG more than before. Do you think the mileage is poor because my daily commute is about 2 miles round trip and the other occasional trips are 3-5 miles long?
  • Eagle BeagleEagle Beagle familEE
    airco ?
  • eldonciv777eldonciv777 Wagonist
    kam3rad wrote:
    After changing the cap, rotor and plugs and a putting k&n filter in I am getting 21.6 MPG, that's about 2 MPG more than before. Do you think the mileage is poor because my daily commute is about 2 miles round trip and the other occasional trips are 3-5 miles long?

    That could be some of it. Have you checked for any codes on the computer? Some things won't set the CEL but will throw a code at the computer. I had a oxygen sensor that eventually set a cel but the code was there for a while. After I switched the sensor I went from 26-30 mpg to 31-36mpg in my 91 rt4wd. Also, if you don't know when the fuel filter was last switched you might want to try changing that.
  • quartersquarters Council Member
    kam3rad wrote:
    Do you think the mileage is poor because my daily commute is about 2 miles round trip and the other occasional trips are 3-5 miles long?

    i think this could be a huge part of it. my wagons act the exact same way when i do frequent short trips. i go from about 34mpg on cross country highway trips to about 25mpg in town. mine is not AWD.
  • lucskywalkerlucskywalker Wagonist
    yes that a defanite, if you had a uego to see a digital readout of your air fuel you would see that air ratio is 11.1 to 12.9 even on a down shift it wont go higher than 15.5. ive been trying to let my car warm up before i drive since the gas is like $4.50 average here in chicago try it out :D
  • B18C5-EH2B18C5-EH2 Moderator
    My mom's 2WD wagon was getting poor mileage and I changed the ECT sensor located just below the distributor (the one with the two wire plug) and her mileage shot up. It never threw a code, but it was running pig rich, especially when cold so that's what lead me to suspect it to be a problem.

    I also later changed out the 02 sensor with an NTK unit - I only use NTK, Denso, or Genuine Honda. NTK 1-wire direct plug-ins can be found for $50.00ish or so online.

    It sucks trying to throw parts at a problem like fuel economy, but unfortumately OBD0 gives us very little in way of diagnostics to locate mpg-related problems when there is no check engine light.

    If you're handy with a multi meter then there are associated tests for every sensor on the car if you want to bust out the Honda/HELM manual.

    BTW have you tried to check for check engine codes? I know it sounds dumb, but sometimes the ECU stores codes for a long time and you may have not seen the light come on at some point. Just check to be sure.

    Besides TW and o2 sensors basically the tune items others have listed should help too. I haven't seen valve adjustment listed so far (maybe I missed it) but valve clearances can have a big affect on mpg too.

    Good luck!
  • Eagle BeagleEagle Beagle familEE
    sheduled maintanance ...
    can have a big affect on mpg too
  • suspendedHatchsuspendedHatch Wagonist
    Use a multimeter and check the O2 sensor for laziness. The procedure is in the repair manual.

    Also do a compression test.

    What PSI are your tires inflated to?

    What "weight" oil do you use? btw don't waste your money on semi-synthetic oil. The synthetic part separates from the organic oil and floats on top while the heavier organic oil is the only thing that gets circulated by your oil pickup.

    Letting your car warm up before you drive nets you 0 mpg the whole time it sits there idling. The best thing to do is drive easy (shift at low RPM) until the engine reaches operating temperature. It warms up much more quickly when it's being driven.
  • Eagle BeagleEagle Beagle familEE
    a picture motorcompartment (underdahood)

    we could look for visual signs for starters

    a sparkplug in this case tells how the fuel is burned

    what do they do when you bring your car for services ?
    right ... they look first :shock:, then examine :roll:

    : )
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