1992 Mazda 323 REALLY low mileage
 

I recently bought an old 1992 Mazda 323 (for next to nothing, so no big loss) but I've found that the car only gets around 190 miles (300 km) to a tank. It's standard, the engine is in really great condition, starts instantly, drives really well, just gets very poor mileage. It has a Jacobs Omni Magnum ignition system installed, which is apparently supposed to make it more efficient.

Are there any Mazda experts who can suggest steps to figure out what the problem might be? I'm a novice and would like to learn a little by looking into this myself and hopefully find the problem before having to bring it in.

First off, revert your ignition system back to stock, contrary to the many reviews one can find on the internet, it doesn't do squat for your engine (or any other engine for that matter). Second, run the tank down to the point where the needle is fully on "E" (to empty out any bad gas you might have), fill it up at a name brand station (Shell, Mobil, Chevron...), take a nice leisurly trip down the freeway for a couple of hundred miles, then fill up again. Divide the miles you've driven by the amount of fuel you've consumed and then apply a ten-percent fudge factor (pumps rarely if ever click off at the same point), and you've got a real number to work with.

Report back to us and let us know how you make out.

Hello,

In addition to the earlier post, you may want to see if the O2 sensor is functioning correctly. There may also be a water temp sensor or ambient air sensor that is out of range for the ECU. These sensors could be sending readings that is making the ECU think is is colder in the engine and outside air actually is. This will cause the ECU to run rich and use up a great deal of fuel. Take a look at the exhaust pipe and see if it is sooty or, better still, look at the spark plugs to see if the insulator looks black. It should be a tan or lighter. Hope this helps.

Thanks for your replies. Sorry for taking so long to get back to you.

I bought the car in October, so the fuel has already been fully replaced. I took it for its first long drive today (well, around 100 miles - my first time out of the city with it) and got much better MPG. I figure I could get about 450km to a tank highway, vs. 300km to a tank in the city.

I went to a mechanic (on the US side) to get my front struts, rotors and pads replaced ($450 all in... seemed like a decent price) and asked them to look into the fuel problem. They said from what they could tell it was likely carbon buildup in the engine, and suggested a treatment with Seafoam. I hate the upsell so I said I wouldn't do it right away, but I've just been looking at these instructions which I might do (thoughts?) http://www.lt1engine.com/tech/how-to...arbon-buildup/

I asked about the ignition, and was told that the built in ignition system is dead, so that's why the addon was put in, though they weren't clear on why the previous owner didn't just spend the $40 for a regular ignition.

The tailpipe blackens my finger, but there isn't sooty material in there, just an oily black coating on the surface.

Spark plugs were supposedly replaced recently by the previous owner, didn't get around to checking the oxygen sensor.

Unless anyone counsels me against it, I might do the Seafoam treatment and see if that improves things before investigating further.

do the seafoam. do a full tune up. get rid of the jacobs add on ..