4 Wheel Drive/SUVs: 98 Jeep Cherokee runs rough at idle

Question
I have a 98 jeep Cherokee that had a bad water pump and overheated.  After replacing the pump, it runs rough at idle.  I did replace the o2 sensor during a muffler change but that didn't fix the idle.  It runs fine at higher rpm but at idle it runs very rough and sometimes cuts off.

Answer
John,

You said that you over heated the engine.  Did you change the plugs, and give it a good tune up.  If you did this, and it still runs rough, I would run a compression test to see if you may have scored a cylinder wall, ruined some valves, or did other damage to the engine.  Depending on how hot it got, you may have warped a head, or ruined a head gasket.

You should consider having an electronic diagnostics on the engine to see if any sensors or other engine components may have been damaged from the heat.

Other components to check are the throttle position sensor, crank position sensor, along with checking all wiring to see if there was enough heat generated to ruin some insulation causing a short.

Carl