Spraying carb cleaner or starter fluid in suspected areas will make it rev up when you find one.

Most common areas are around intake manifold, throttle body, or brake booster fittings.

Why do you think you have one?

 

Yeah. I get hesitation, but only during medium throttle. I'm trying to figure out whether it is a vacuum leak or the Throttle Position Sensor, which seem to be the best candidates so far.

How do I spray carb cleaner while I'm driving the car? It doesn't hesitate at idle or if the car is not under load.

 

Obviously you don't check for a leak while driving. This does not mean there is not a leak while at idle. so you check at idle and if you don't find anything you move on to TPS or Mass air sensor. I assume the check engine light is off?

 

In my case, it was worn out spark plugs. I seem to have gotten counterfeit NGK Iridiums that wore out in less than 20,000 miles.