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20r engine 13 MPG?!?!
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* March 10, 2007, 12:36:56 AM
My 79 toyota pickup is costing me too much for gas.  I don\'t use it much but when I do, I know I\'ll have to be willing to pay through the nose!

Here are the symptoms:

1. The air filter gets clogged really quickly with a black soot.
2. It backfires and puffs out a little cloud when I shift from first to second.  Sometimes it does this when shifting in the other gears.  Sometimes it backfires when I back off the gas.
3. It gets really bad gas mileage.  I was hoping for at least 20 MPG.

Other than this it runs pretty good!

I\'d say it sounds like it is running rich but I couldn\'t find a mixture adjustment in the Chilton\'s manual.  All I could find was a backfire valve.

I\'ve already replaced the plugs, wires, and even the distributor (my son knew of a junker celica with a 20r).

Any suggestions?

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* March 23, 2007, 07:44:51 PM
#1
Probably time to rebuild the carb on that engine.  Backfire can be a function of an off air/fuel mix, bad jets int eh carb, poor atomization of fuel, timing is off. or valvetrain is damaged.  The 20R uses a timing chain that generally will last the life of the vehicle, but has to be checked every once an a while for chain stretch or worn chain guides.  Also keep in mind that the 20R is an interference engine, meaning if the timing gets too far off or the timing chain breaks - you will probably end up destroying the valves/valvetrain/piston tops in the process.

First I would double check the timing, then the air/fuel mix.  Try cleaning the carb first to get any deposits off then start thinking about getting it rebuilt.

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