I bought a 2001 trooper not to long ago knowing it needed some engine work. So I took the trooper to a well known mechanic in town and he assured me it needed a motor. I ordered a slightly used motor and Had this guy put it in. The prob is: the vehicle starts and idles like a new one. whenever you get out on the street in it it acts like it has no power and almost sounds like it choking a little. I took it to the muffler shop and he said the muffler and exhaust were all clear. It also shifts very hard going from 2nd to 3rd and back from 3rd to 2nd. If you get the trooper going down the street and gas it it will only get to around 2500 rpm and wont accelerate any more. it just keeps cutting out, although it has worked somewhat since i had the motor replaced.. occassionaly you can get in it and punch it and it will almost drive like normal, but its never for very far then it starts cuttin out again. I also changed the fuel filter and the fuel pump and still has the prob...PLEASE HELP

 

also forgot to include if it matters...if you are in park in and have the vehicle running and stomp on the gas it will not rev up like it should. even with the gas to the floor it will only rev up to around2500..but not constant. it goes up and down...from like 1800 to about 300...no higher

 

If the timing belt was ever replaced, it could be off a bit. Getting it right is a very tricky on the 3.5.