Jeep Wrangler TJ Engine Low Power

I Have A Jeep Wrangeler 4.0 L 1999 I Am Having Trubel Whith Lose Of Power On Hills I Am Haveing To Put It In 3rd On Hills That I Used To...

I Have A 97 Jeep With The 4cly And When Im On The Freeway It Is Hard To Get Up To 70-75 And When Ever I Go Up A Smalll Hill Or Go Over An...