Idle revs and drops

Girlfriends vehicle:

94 Hyundai Elantra

Its a beater that was just given to her. I've started going through it looking for what needs to be fixed.

One issue is that the rpms rev and drop as if its searching......but heres the kicker....it only does it while driving, or as you come to a stop in between driving. If you start the vehicle, and just let it sit, it idles fine. No jumps or drops in the idle at all.

I went ahead and put a new air filter on it (which it was definately in need of), as well as cleaning the throttle body, and all the electrical connectors for MAF etc. Checked for vac leaks, which I found none.

I'm assuming its either the 02 sensor, or some other sensor.

Is this a common problem? Anyone have any helpful hints?

thanks!

I've pulled the connector on the Idle Speed Control Sensor (which is just below the throttle body at the 6oclock position.

$600 part! Ugh.

Time to look at a junkyard!

You can also checkout Hyundai webtech for any TSBs etc.

TS out

Josh, if I understand your description of the problem, mine does the same thing. You give it gas for a short spurt, then let off. You expect the RPMs to drop off right away, but they don’t. They stay up there, as if you still have your foot on the gas, for several seconds. Same problem?

If so, I _think_ it’s not a problem. I _think_ it’s some damn emissions control program. I had an old Pinto that did the same thing, using a vacuum sensor hanging off the carb. And now, twenty-five years later, my Elantra does the same thing.

I’ve asked the local Hyundai techs about this, and they just look at me like I have two heads.

Girlfriends vehicle:

94 Hyundai Elantra

Its a beater that was just given to her. I've started going through it looking for what needs to be fixed.

One issue is that the rpms rev and drop as if its searching......but heres the kicker....it only does it while driving, or as you come to a stop in between driving. If you start the vehicle, and just let it sit, it idles fine. No jumps or drops in the idle at all.

I went ahead and put a new air filter on it (which it was definately in need of), as well as cleaning the throttle body, and all the electrical connectors for MAF etc. Checked for vac leaks, which I found none.

I'm assuming its either the 02 sensor, or some other sensor.

Is this a common problem? Anyone have any helpful hints?

thanks!
it has to be the o2 sensor,im pretty sure

Might try replacing the throttle position sensor. Had the same problem, that cured mine.