Loss of gas mileage

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  #1  
Old 07-02-07, 07:25 AM
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Loss of gas mileage

My 1996 Ford XL 150 is a 6 cyl and is not getting the mileage it should. I have changed out the fuel and air filters and readjusted the timing which was off. It still is not where it should be. Any suggestions?
 
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  #2  
Old 07-02-07, 08:33 AM
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Join Date: Sep 2004
Posts: 238
lots of things

Why was the timing off? Did you follow the instructions on the emissions label? Check again.


Often overlooked are tire pressure, t-stat (make sure it runs at design temp not cooler) and harder to diagnose, fuel injectors that no longer have the nice spray pattern they started with. The injector idea only works, if you use more gas to do the same diving, so you must be dumping unburned gas, which should make you fail tailpipe tests and maybe set the CEL. Another possibility is the egr system may not be working right. If you donít have enough egr your computer will retard the spark to avoid knocking and to get the same power you need more throttle. Again, I would hope you get a cel.

While you are thinking about it you could look at plugs and wires (cap and rotor too if you have these) but your car should again set a CEL with a miss. Another classic fishing move at this point is to clean the MAF sensor.

Do you ever smell gas? Do you every see a yellowish build-up on injectors or fuel hose fittings? If yes look for fuel leaks. Figure out how to use a jumper wire to make your fuel pump run for 45 minutes w/a stone-cold engine and look for wet spots.

Are you using the correct oil?

Are the tires correct?

No aftermarket crap under the hood or on the exhaust?

Check you idle speed. You probably cannot adjust it, but it may be to high if one of the many plastic check valves or restrictors in the vacuum system is broken or missing. I broke a tee on a car once that had restrictors built into it that I didnít notice until it idled to fast after I installed a universal fitting.

Look at you brakes make sure you do not have a seized caliper or dragging parking brake.

Empty the crap out of the back, turn off the ac and drive slower.

Do a compression test.
 
  #3  
Old 07-02-07, 10:12 AM
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Location: Cape Cod
Posts: 4,320
The computer re-adjusts the timing, even if it's off
Make sure you followed the proper procedure for this particular engine, which may include removing the SPOUT connector near the distributer, and have the correct specs (there's timing and total timing specs)

Aside from the other basic tune-up items such as plugs, wires, filters, cap 'n' rotor, there's a few other things to check such as fuel pressure
...and the O2 sensors (Oxygen sensors)

The O2s are high on the list for increased fuel consumption
As they get older (well, more miles) they lose their effectiveness, causing the engine to run rich, further fouling the O2s...confusing the computer into making the engine run rich...etc...

Although they can be tested, if they have over 60,000 miles on them, then IMO it's not a waste of money to replace them anyway
They are not working as well as they should

Also, make sure your tire pressure is correct, and your steering and suspension isn't failing somewhere, both these can increase fuel consumption
 
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