1996 grand cherokee starts fine and runs great the first 5 minutes. Then it runs like ****..doesn't completely stall but runs really rough. Like it wants to stall but doesn't. Replaced the fuel pump and...
First thing is; When you changed the fuel pump, did you compare the 2 to see if they were identicle?, because it's possible that you could have the wrong fuel pump.. Second; you should have changed the fuel filter when you changed the pump, if not? you need to put a new fuel filter on... Third... It is possible for the upper o2 sensor, because on your Jeep, you have an OBD II system, which is, ( On Board Diagnostics II) and that system uses two "o2" sensors; One before the catalytic converter and one after the converter. The Primary o2 sensor is the one before the converter; The secondary o2 sensor, or catalyst monitor, is located after the catalytic converter.
The two o2 sensors work on an "open loop and closed loop". When the motor is cold, the o2 sensors are in open loop, which means they are not being used to monitor the exhaust gas, and when the motor warms up- after 5 minutes or so, then the computer switches to "Closed loop" and the o2 sensors are then used to monitor the exhaust gasses, so it is possible that your primary o2 sensor, or the one before the catalytic converter is bad.... But! It's very rare for both o2 sensors to go out at the same time.... I hope that answers your question & gives you an idea of how the o2 sensors work in conjunction with the fuel injection system.
Apr 29, 2010 |
1996 Jeep Grand Cherokee