2003 Buick Century Car Intermittently Won T Idle Down Times Runs 65 Mph Without

2003 BUICK CENTURY
200,000 MILES
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Car intermittently won't idle down. at times runs 65 mph without
foot on gas pedal.

I have had the transmission checked (nothing wrong); disconnected the Cruise control, the only code display is PO446 Evap Control system which has been showing for 2 years. We replaced every sensor, took the Evap canister down, even replaced gas cap, nothing cured it. so I just drove it with engine light on. What is the problem?
Mar 28, 2013 at 1:42 PM
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JDL
  • ✓ASE Certified Mechanic
  • 16,098 POSTS
  • ASE Certified Mechanic
Block off the mouth of throttle body, see if it has any effect on the idle? It should kill the engine. If no effect on idle, look for a vacuum leak.
Mar 28, 2013 at 8:12 PM
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