Hi, My names Mark and im new to the forum. My dad just bought a 97 Jeep Grand Cherokee from a guy and the engine was shot, Blown head gasket and such along with bad transmission. So he took it to a mechanic who found a Engine and trans out of a 2001 and installed it but put all the electronic stuff on the 2001 engine that came off the old 97 (I guess there Interchangeable) But it has a problem now and the mechanic cant figure out what to do. (Shadetree Mech) So we brought it home and are going to try and figure out what it needs. Anyways what it is doing is it Cranks and runs but will not idle. It surges a couple times then dies unless you keep your foot on the gas pedal and once you get rolling it does fine. We changed a sensor on the throttle body i believ it is the throttle position sensor but it didnt help. I noticed there are three sensors on the throttle body One is right in the throat and there is one next to it and then another on the Intake manifold. We changed the one that is directly center of the throat is this the throttle position sensor? and if so do you think it could possibly be one of the other two sensors have went bad?
also what are these sensors called?
thanks for any help you can provide its appreciated

 

There are only two sensors and one actuator on the throttle body. The actuator is the Idle Air Control motor, it regulats the idle speed and adjusts when needed. The IAC motor on your engine may be shot. Some will tell you to clean it, but just replace it instead.

 

Thanks Busted, I went ahead and changed out the IAC and the Throttle Position sensor and that didnt help, then i found that the wires coming from the Oxygen sensor on the exhaust had melted against the exhaust (The Mech must have left them hanging) so i clipped the wires and connected them back together using splices and heat shrink and it still doesnt help. Im wondering if the wires getting hot like that did it burn the oxygen sensor... I know the oxygen sensor gets really hot since it is mounted in the exhaust but not sure if the wires burning would have shorted something.

 

Welcome to CF Mark.
The Intake Manifold Air Sensor location is in front of the throttle body on the '01, behind it on the '97. Make sure all vacuum lines are hooked up, and none are broken.
The Throttle Position Sensor is on the rear of the throttle body.
The Idle Air Control Motor is on the passenger side of the throttle body.
The Map Sensor is on the drivers side of the throttle body.