zyou tps might be bad
Check your engine thermostat, it maybe stuck open, keeping the engine from dropping off high idle
why does my 4.75 BRIGGS & STRATTON lawnmower engine idles high and low when cutting my grass
throttle posistion sensor or vacuum leak
On my Chevy truck it idles high when its low on antifreeze but if its not that more than likely its usually a vacuum line loose or cracked. good luck.
Have vehicle scanned to determine the problem
I have 91 chevy k1500, It does this, Sometimes it will idle a few minutes, then jump to high idle and check engine light comes on, And sometimes its as soon as i start the engine... I was told it was a vacum leak, But im no mechanic
First check your throttle body sensor and then your (iac) motor. Last but not least it could be your plenum gasket or a leak in your vacuum system
FORDS ARE A poc
You may have a vacuum leak, check the gasket under the throttle body, spray some carb cleaner around the base of the throttle body while the engine is running. If there is a leak you will hear a change in the engine rpms.
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High idle, misfire, check engine light,High idle, misfire, check engine light,
cold engines hve high idles because the pcm is dumping fuel into the motor in order to increase engine operating temperature. when speified temperature is reached, the amount of fuel is decreased an the rpm drops down to the lower idle speed