after a front end collision, my JEEP (4.0 6 cyl. 5 speed manual) engine races at a high rpm when started, and will not slow down

Check to make sure you don't have a huge vac leak somewhere. A front end collision could have ruptured many vac canisters such as the vac reservoir, the purge canister, the brake booster, or even the intake manifold itself could have been cracked.