I have a 2009 Jeep Grand Cherokee with over 200,000 miles on it .It get regular oil changes and maintenance. I filled my gas tank and started driving home,was 3 miles from my house and when I tried to go faster than 40-45 mph my car won't go any faster, even whe I put my foot all the way on the gas.What might it be?
could be one of several things, could be a bad oxygen sensor, throttle position sensor, cam or crank position sensor, or clogged fuel filter, I would go to a local automotive parts store and ask to have them check to see if there are any computer codes which will tell you which if any of the sensors are bad, usually it's a bad or unhooked oxygen sensor. any of the parts stores usually most do it for free, like advanced auto parts, auto zone, or any major parts store.
Once you pull the DTC(s) as John8297 suggested, Chilton has diagnostic information for the 09 Grand Cherokee. Find it in the navigation outline section, "Diagnostic Trouble Codes." You'll need to identify your specific vehicle by engine size and VIN code. If needed, go to "General Information and Identification" to understand the VIN (vehicle identification number).