Mechanics

LEXUS SC 400 ENGINE PROBLEM

1993 Lexus SC 400 • 107,000 miles

My dad has had this car forever however it sat in his back yard for about 7 years I'm finally getting it smogged registered cuz He gave it to me for graduation it was started up maybe once every other month so it didnt get dry rotted or rats didnt ge in the engine I drove it to the smog shop it's a really clean car everything passed but the emissions the guy said it was giving out to much gas at 15 mph and not enough at 25mph put a new fuel pump battery air filter and oil change / oil filter can someone maybe figure that out so I can get this beauty back on the road
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Guest
March 17, 2013.



Dry rotting comes from sitting, especially on grass. You don't prevent that by running the engine once in a while. Mice only need one night to chew through wires. You won't scare them away by running the engine once in a while. That will attract them. They like to be warm.

The fuel usage refers to "fuel trim" numbers. The Engine Computer will learn those correction numbers while the car is being driven. As you're driving, the computer watches the readings from the oxygen sensor(s) and makes small adjustments. Those are called the "short-term fuel trims", (STFT). When it sees that it is constantly having to make the same corrections, those numbers become part of the "long-term fuel trims", (LTFT). The long-term numbers are what it starts out with each time you start the engine. They are programmed in at the factory to provide a rough starting point, but every car needs a little correction at various speeds, altitudes, engine temperatures, etc. It sounds like that memory was lost, typically from disconnecting the battery or letting it run dead. Those numbers update as soon as you start to drive it.

Caradiodoc
Mar 17, 2013.