After reading question after question on fuel economy, I thought I'd at least collect a few common solutions together to help reduce the number of repeat questions.
Possible Solutions:
1) Check the quality of your spark plugs. Ensure you are still gapped to the correct setting. Also make sure there is a good point on both ends of the electrodes and that it isn't pitted from detonation.
Also, check for excessive carbon. Excessive carbon is an indication of bad burning. If you're getting this, also check if the heat range is correct. It may be too cold
2) Check the leads. A good set of leads should be about 5000 ohms. Racing leads are about 2500 ohms. Tolerable is 10,000 ohms. . Anything over that, get a new set
3) Check your dizzy. If the buttons are worn or corroded, replace them
4) Check your timing. If you retard your timing too far, or advance it too far, then you will lose fuel efficiency
5) Check/change your air filter. If it's clogged, you can upset the Airflow sensor, as you start creating negative pressure in the intake, before the throttle plate.
6) Check/change your fuel filter. If it's clogged, it could be making fuel drip in instead of spray in. This reduces burning efficiency and makes the ECU compensate by putting more in.
7) Check your fuel pressure. If it's too high, you will be spraying in more than you need to. If it's too low, the same as a clogged fuel filter results
8) Check your injector spray pattern. While theoretically, you could rig it up yourself to test, it's pretty cheap to get them ultrasonically cleaned with testing before and after. I think it's like $30 per injector at Ruf Performance, Ingleburn.
9) Check your water temperature sensor/thermostat. If your engine isn't getting up to heat, then the ecu will continue to dump excessive fuel in, thinking the engine is cold
10) Check the oxygen sensor. If it's fouled, your ECU might be doing all sorts of silly buggery things.
11) Check your cold idle valve. Make sure it isn't stuck open and causing more fuel to go in.
Things should roughly be checked in that order, not really because of likelihood, but because the easiest checks are listed first.
If anyone has any more, please feel free to add them.
Oh, finally, if you're using your Odometer to estimate fuel consumption, make sure it isn't "sticky". I know someone who thought they were getting 200km out of a tank, but really, their odometer would freeze then next time he went over a bump, start turning again. He was actually travelling 400km on a tank, but his odometer only registered like half that on average.
Hope this helps
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