high idle

[moparstables]

The car starts great and idles good but after driving for 30 minutes the car won't idle down. It wants to idle at 1800 rpm. After the car cools down and restarted it is back to regular idle. Any ideas?

 

[challenger6pak]

Could be a sticking vacuum advance unit or a vacuum leak anywhere in the system.

 

[burntorange70]

Hi idle sticking and not pulling down to the low idle after warm up? Or the choke. Do you have mechanical or electronic choke?

 

[Chryco Psycho]

Exactly ........ what carb , choke system , electric or heat stove , linkage binding , vacuum leak etc could all be causes ?

 

[moparstables]

I am running a holley 3310 850 double pumper with an electric choke. I don't have the high idle set on the choke. I do need to check for vacuum leaks.

 

[moparleo]

Check to make sure that the throttle plate is closed completely when at idle. Engine should just about stall if it closes completely. If not, cup your hands over the airhorn to block off air to the carb, if the rpms increase you have a major vacuum leak for sure. If you have a set of bake line pliers, clamp off the power booster line to check for rpm change also clamp pcv vale hose to check for a pcv valve sticking open. If you still haven't nailed it down use an aerosol bottle filled with water or Windex or any other non flammable liquid and squirt along the intake manifold where the ports mate to the heads. Along the carb base gasket and any other vacuum sources. Do not use Carb cleaner or any other flammable. Use common sense. Why would you spray something that can catch fire on a running engine? The whole point is to make an rpm change at the leak source. Carb cleaner will increase the rpms and water will lower the rpms same test result.

 

[moparstables]

I will try that. Thanks

 

[moparleo]

I will make one addendum, that you can also use a bottle of propane and a rubber hose. Propane gas is heavier than air so you can "pour" propane over the manifold and other possible leak sources and get an idle speed increase. Much safer than other combustables.

 

[moparstables]

I will try that also if the water don't show anything.