It is a 1992 Elantra, early production. I have been fighting low
power at low RPMs and a pulsing/bouncing idle, also, the idle
speed
seems to vary alot after it has been driven awhile. I checked the
output from the air-flow sensor, and found it REALLY jumpy at
idle,
how smooth is it supposed to be? The computer was replaced (the
old MITS one crapped out) The car just drives weird with low
power...
Are there any mods to make on this car to improve it to the later
1992 ones?

Thanks for any info as always,
AJH

 

There are no siginificant differences between the early 92 and later 92
vehicles. In fact, I don't recall any, but I'm sure there are probably a
couple.

The bouncing idle is caused by too much air entering the engine. The
computer begins shutting off the injectors in an effort to slow the engine
down. As the injector pulse starts/stops, the engine revs up and down,
causing the bouncing. I've seen improper repairs where the throttle was
pulled open by adjusting the throttle cable on cars which were stalling.
This will cause the bouncing condition you describe. Check your throttle
cable to be sure it isn't holding the throttle plate open. Check the air
bypass screw to be sure it isn't allowing too much air into the engine.
Check your idle actuator. It screws into the bottom of the throttle body
and has a six pin connector with two rows of three pins. If I recall
correctly, the resistance in each row between the center pin and each of
the outer pins should be about 30-35 Ohms. If the actuator doesn't work
properly, it could cause the bouncing idle. If it's shorted, it WILL blow
up the computer. An open circuit just won't work, but won't kill the
computer.

The air flow readings are jumpy at idle because your car isn't idling
steady. The air flow readings should be steady, but so should your rpm's.
Address the rpm's first and the air flow readings should follow.

Low power typically has nothing to do with idle settings. Can you tell if
the car's misfiring? Low rpm lack of power issues tend to be caused by
ignition misfires. If you're misfiring, I'd check the plugs, wires, and
coil. Does it matter whether the car is cold or hot in terms of the lack
of power? Does it matter how fast you're going?