engine is revving to 300 rpm when turned on, what is the problem?
could be your throttle position sensor or a vacuum leak
X2, if your throttle cable was out of alignment it would constantly run high, the vac system does a lot of work at engine start. A (hill billy) way to check for a vac leak is to spray water over the vac lines and watch for bubbles or smoke a cig.
Looking for a Used Wrangler in your area?
CarGurus has 19,082 nationwide Wrangler listings starting at $3,000.
Search Jeep Wrangler Questions
Jeep Wrangler Experts