Q: My jeep wont go over 35mph. 2001 Jeep Grand Cherokee

Hello - if this loss of performance was rather sudden (i.e. overnight or within a week or so), a failed throttle position sensor or fuel pump could be the problem. If this happened gradually, over months lets say - this could be a clogged catalytic converter. Check for problem codes first, even if the Check Engine light is not illuminated. I would recommend a loss of performance inspection by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, give you an accurate assessment of damage and cost estimate for repairs.