Quote:
Originally Posted by AndrewJ
After an elevation gain of 1800 feet in 20 miles or so, the car started acting kinda funny.
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That much of an elevation change in such a short time while the car was running will make it not run right.
Our Civics use a speed density system to calculate airflow into the motor. The elevation change was enough that the pressure decrease skewed the fueling and timing.
Next time you make that trip, when that starts to happen....pull over, shut off the car, turn the key to the run position and wait until the check engine light goes off, then start the car.
During that test period the car checks the voltages on all sensors. The voltage that it reads on the MAP sensor is deemed to be the atmospheric pressure for the outside of the car. Then the computer has a lookup table based on atmospheric pressures for fueling and ignition advance.
This process used to be printed in the owners manual for fourth generation civics, but for some reason I don't see it too often in the US manuals.
Hope that helps.
