Why dose the engine idle high after being fully warmed up

This is normal. The ECM monitors engine temperature and increases idle when it sees the engine is cold. The ECM sets the idle back to normal when engine temperature rises.

This is normal. All vehicles idle high at start up to get the engine to operating temperature. This is known as open loop. The computer ignores signals from O2 sensors to keep your engine running safely. Once it has warmed up, it will enter closed loop, and you will see a decrease in idle.

sounds like your air intake gasket is leaking. If you take ether, or brake cleaner and spray it where the air intake is bolted on, the idle will come down to normal. Is this problem existing even after the engine is warmed up, or just when you first start it up?

Hi,
You need to get your engine coolant thermistor checked and tested. This is what tells the ECM when the engine temperature is at normal working temperature and turns the idle down.
But when the idle won't come down from cold to warm this is usually the main fault.
Hope this helps.
Thanks
Jason

Its most likely a vacuum leak or the throttle needs to be adjusted. Check that there is a small amount of play in the throttle cable between the bracket on the back of the intake manifold and throttle body. If there isn't, the throttle body may not be closing all the way.

Other possible causes:

The coolant temp. sensor is giving an incorrect reading. When the sensor reads a low coolant temp., like when you first start the car and the engine is cold, your idle will be high. As the engine warms up to operating temp (about 200 F) the idle speed will decrease. Idle speed should be around 750 rpm when the car is fully warmed (800-850rpms fully warmed with a/c on).

The idle air control motor may be stuck open.

Hello,
The car may be hard to start because it may need a normal tune-up. If the spark plugs are pretty used, they will slowly stop burning as much fuel because the spark slowly gets lesser and lesser. On a cold day the fuel is harder to ignite with a small amount of spark.
Normal idle when its cold means that your cars idle is probably too high. If you lower the idle, the choke on a cold day will keep the idle a little higher until the motor warms and then it will kick back off. If the idle is too high, it will run very rich, smothering itself with fuel, and causing the idle to stay low. When the car warms, its creating better spark when its warm, and with the idle being too high its running at a fast idle.
The car wont start sometimes can be the cause of a few things. If the ground is bad on the fuel pump, it wont make a good connection sometimes for when you turn the key on, the fuel pump dont pump the fuel to the engine. Another one can be that your accessory switch can be loose going to the fuel pump. I think its your ground though. Good luck! Hope this helps.
Have a nice day. -Steve

The high idle speed at start up is normal. As the engine temperature increases, the engine idle should kick down automatically. Insofar as the emissions results, if there were a problem, the check engine light should be on. If it is, take the car to an autoparts store and have the fault codes read. Most parts stores will perform the scan for free. If the check engine light is not on, and the idle question was all you were worried about, you are good to go! Hope this helped and best wishes.

this is normal for a car of this age
carburetor type motors have a automatic choke
this is activating when you start your car as it is so cold
i would not worries about it
it is designed to make it easier to start your car when it is cold my car dose the same thing
hope this helps
ricko

take your car for a tune up
if they are carburetor type motors you may need your carbie cleaned and a tune up
if you clean it your self with carbie cleaner it may increase in idle speed this is nothing to worries about it is a simple adjustment
with a carburetor type motor they tend to idle higher when their cold this is the automatic choke kicking in and normally it should happen till the car is a bit warmer and the accelerator has been depresses
although a car should idle at 800 rpm my paddok car dose when it is cold it idles at 1200rpm i like it this way as the car warms up quicker as i will not drive a car while it is cold
hope this helps
ricko

The high idle is caused by the choke and the high idle on the carb. It is working normal and you do won't to warm up this motor before going. When it is warm and you hit the gas it activates the choke pull off to bring the idle to normal. Your mechanic is used to fuel injection that will control the fuel/air mix according to temp. I still let my injected cars warm up so the oil can thin a little. If you jump on the highway with cold thick oil it can all wind up in the to of the motor.