Hyundai Repair: 99 Hyundai Elantra Gls Manual trans Cold stalls, hyundai elantra gls, coolant temperature sensor

Question
Every morning when I go to take off in my Elantra, When it is cold the cars wants to stall unless I feather the throttle or the cars wants to stall. I t never usd to do this. I have had the pluygs changed and wires and also the fuel filter. It only does this when cold. It makes shifting very dificult because when you shift from first to second and try to give it throttle it wants to die. And if you floor it it will stall go stall go then finally pick up and go. HEEEELLLPPP!!!. Dustin Boise idaho

Answer
If your check engine lamp is coming on, absolutely start there.  Your idle is controlled by the computer, so the cause of the check engine lamp is likely the same as the reason for the failure to idle properly.

Failing that, you'll want to do the following:
1.  Check the throttle cable to make sure it has slack in it.  If the throttle is held partially open, the computer may not realize it needs to idle the car.
2.  Check the idle switch (if equipped -- it'll depend on the production date of your car).  If the switch is open when your foot is off the gas, the computer may not try to idle the car.
3.  Check the throttle position sensor.  If the sensor reports incorrectly that the throttle is open, the computer may not try to idle the car.  
4.  Check the coolant temperature sensor.  If the sensor isn't reading the coolant temperature properly, the computer may not attempt to idle the vehicle fast enough or richen the mixture enough.
5.  Check the idle actuator.  If the condition is occurring, you can try whacking the actuator with a medium sized wrench-- not too hard; you don't want to break it, just jar it a little.  If that makes the problem go away, the idle actuator is sticking.

For items two, three, and four above, it'll be easiest to check with a scan tool.  I'm presuming you don't have one and would need to take your car to a shop for that type of check.  For service information and specifications on these sensors, register for a free account at www.hmaservice.com (requires Internet Explorer).  There's a wealth of information at the site, including the service manuals, schematics, and technical service bulletins.  For example, TSB 99-36-011 explains that Elantras produced after 5/30/99 no longer use the idle switch and instead use only feedback from the throttle position sensor.