High idle

[Ronnie Grassel]

Idle goes from normal to high ,back and forth .
when jeep is in gear the high idle leads to increased acceleration .with no deviation to the gas pedal ?

 

[Jerry Bransford]

A high idle is pretty much always going to be caused by a vacuum leak. Has any work been done on the engine, especially where the intake manifold or throttle body is concerned?

There are vacuum lines all over the engine compartment and at the HVAC system. Spraying the vacuum lines, couplings, manifolds, etc. with something like throttle body cleaner can often find the source of the leak when the vacuum leak sucks the cleaner in through itself and into the engine causing it to stumble.

Here are the engine vacuum lines... item 8 is the vacuum reservoir. There's a big vacuum line that connects between the intake manifold and power brake booster too that isn't shown.

 

[Ronnie Grassel]

A high idle is pretty much always going to be caused by a vacuum leak. Has any work been done on the engine, especially where the intake manifold or throttle body is concerned?

There are vacuum lines all over the engine compartment and at the HVAC system. Spraying the vacuum lines, couplings, manifolds, etc. with something like throttle body cleaner can often find the source of the leak when the vacuum leak sucks the cleaner in through itself and into the engine causing it to stumble.

Here are the engine vacuum lines... item 8 is the vacuum reservoir. There's a big vacuum line that connects between the intake manifold and power brake booster too that isn't shown.

View attachment 197195

thank you . will look into this when i get home .

 

[CharlesHS]

Check the 1/2" vacuum line going from the engine to the brakes vacuum booster.
Pull the hose from the vacuum booster and plug the line and IF the engine RPMs return to normal; the vacuum booster has a leak.
IF the engine RPMs don't decrease; the problem could be a leak in the intake manifold gasket or the throttle body gasket.
You can use a spray bottle of water to locate the source of the leak.