Where to start

Discussion in 'Start Your Journey Here' started by blitzkraig, Mar 25, 2008.

  1. blitzkraig

    blitzkraig New Member

    Hello all. This past friday I became the proud new owner of a 92 Civic HB VX manual. It's got 203k miles but still seems to be in decent shape. I have a feeling the motor is not quite up to peak ability (keeping it's mileage and wear in account). I'm at a little less than half a tank and the trip odometer says 200 miles. The previous owner put an aftermarket Ingen air intake and a DC exhaust header on the car. He gave me all the stock parts so should I swap the stock air intake and exhaust back on? After that is there a way to test the oxygen sensors? Should I replace the catalytic converter? Anything else I'm missing? I just thought of spark plugs, so obviously there must be more. I'm dedicated to getting max efficiency from this little bugger! Thanks!

    - 92 Civic VX
  2. Skwyre7

    Skwyre7 Well-Known Member

  3. 93Hatch

    93Hatch Well-Known Member

    I have a 93 HB, but mine is an auto trans. I should have got a 5 speed, but mine was a good deal, and its a temporary deal. Where do you live? If you happen to live in southeast VA I just got the Haynes manual for the car. Also my neighbor has a diag scanner that he said I can use. On the newer cars a bad O2 sensor will trigger the CEL, but I don't think it will for the older ones. Definitely check the spark plugs. Mine had oil down the spark plug wells. A valve cover gasket set will fix that, and is only $31 from Advance. The intake and exhaust shouldn't hurt your FE as far as I know, but not sure. Those items just make it hard for teenagers to drive slowly. I was at half a tank at 200 miles, so with a manual you should get more. I think you can squeeze more mpg out of that car. Have you inflated the tires to max sidewall psi?
  4. some_other_dave

    some_other_dave Well-Known Member

    Welcome to the forum!

    I doubt that the header will hurt your FE; it may even improve it slightly, depending on how restrictive the stock exhaust is. If the intake is a "cold air" type, consider a "short arm" or "short ram" (depending on who is talking) to draw warm air from the engine bay.

    I don't know offhand of a way to test that the O2 sensor is working correctly, other than to check it against another O2 sensor that is known/presumed good. Your car will throw a CEL if he O2 sensor isn't working at all, or is unplugged, or (I think) if it constantly detects a very rich or very lean mixture.

    A good tuneup (new plugs, wires, cap, rotor; new fluids; valve adjustment, etc.) will help make sure the engine is running at its peak efficiency, and that will help with FE. Of course, upping the pressure in the tires (to the MAX number on the sidewall, though some run more) will help. If your engine isn't leaking too much oil, going to a light-weight synthetic oil (e.g., Mobil-1 0W20) will also help your economy slightly.

    And, of course, the biggest thing is: Slow down! Drive the speed limit, or a bit slower if that is safe and practical, and your economy will go up.

  5. atlaw4u

    atlaw4u Well-Known Member

    Welcome to the forum and I agree with the above.

    The exhaust will probably not hurt fuel efficiency but it may be hurting you in the low-end torque department. Also, I'm not well versed in the VX but I beleive it was Honda's earlier attempt at improving lean burn for increased fuel efficiency and thus, your aftermarket intake will probably hurt your fuel efficiency as it is bringing cooler air in. Lean burn engines run better with warm intake air. You should get some base MPG numbers and then reinstall the original air intake to compare.

    You may also want to do a search for warm-air modifications on this and other MPG forums tol see what I am talking about.
  6. blitzkraig

    blitzkraig New Member

    Well I got to do my first fill up and I'm getting about 34 mpg. Not too shabby, but could be better. I noticed for the first time since I picked the car up that there is an ominous bluish smoke following me at times, indicating oil burn. I'm going to check the compression in the cylinders this weekend and just pray the oil is from worn valve guides and seals. Once the oil burning issue is dealt with I'll replace the spark plugs and change the air intake back to stock and see where my mpg is then. Thanks for all the advice so far!

    92 Civic HB VX
  7. 93Hatch

    93Hatch Well-Known Member

    Its a very easy thing to pop the plug wires off and see if there is oil down there. That will zap your mileage. Something you can do while filling up, but you'll be done filling up before your down checking though. When I popped the plugs out the oil drained down into the cylinders (what I couldn't get with a shop rag anyway). Then I cleared the neighborhood of mosquitos with all the smoke.

    Note to self: roll the car out of the garage first next time!
  8. shifty35

    shifty35 Well-Known Member


    You seem to have picked yourself up a classic FE weapon! My thoughts below...

    Please replace the aftermarket components with the stockers ASAP. The intake pipe diameter will be way too large with the Injen style intake. In addition, the aftermarket header will replace the OE catalytic converter, so you are effectively running without a cat.

    The oxygen sensor should have 5 wires in it - if not, the engine may have been swapped out - check to ensure you have a D15Z1 - the engine should be stamped on the front, to the left of the header, right next to the transmission. You may have to clean the plate off if it has gunk on it. These cars are very popular for swaps. If it seems to have any pick up at all, it may not be an original VX. Also, check to make sure that the spark plugs are on the exhaust side of the intake manifold rather than the intake side (if this makes sense...) There should also be a VTEC solenoid on the intake side of the engine, as well as a canister-looking EGR valve mounted to the intake manifold.

    If you have blue smoke, you are looking at worn valve seals or worn piston rings. Either is not a terrible prospect, as both are fairly inexpensive to take care of. A compression test will tell you the inevitable, you will likely need a leakdown test to determine the source of the problem. Both will contribute to a poor combustion chamber seal and ultimately damage FE.
    The trick to getting high MPG at first in a VX will be learning to keep it in "lean-burn" mode. This will mainly involve keeping a very light foot on the throttle. I could relate my experiences with lean-burn in the Insight, but they might not be helpful without an iFCD to look at.
  9. some_other_dave

    some_other_dave Well-Known Member

    These days, many or most headers keep the catalyists intact. But as was mentioned, they may be trading off some low-RPM torque for high-RPM power, and you don't really want to be driving at high RPM if you're trying for max FE.

  10. blitzkraig

    blitzkraig New Member

    The engine stamp was the first thing I checked when I looked at the car. I'll check for the other things that were listed and swap the stock parts back on. Haven't had a chance to check the compression cuz my dad has borrowed the car for a week while he's visiting from out of town. I plan on having a friend of mine help install a little LED light on the dash to indicate when lean burn mode is in effect. If anyone's interested I can post a little article on how it'll be done.


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