My 2002 sport has 23k miles and idles like ass.  When I first start it up it sounds like  the motor is going to shut off. the whole thing shakes horribly.  My 100k xj didn't even do this.  I'm using mobile 1 synth.  I DON'T use cheap gas.  Any ideas.  Injectors?  Already I've had to replace the head gasket.    

Is there such a thing as CHEAP gas, at over $4/gal.?!?! Did it start doing this after the head gasket was replaced or did it do it before that too?  

You could have a fouled O2 sensor. The Throttle Position Sensor (TPS), Coolant Temperature Sensor (CTS), Manifold Pressure/Vacuum Sensor (MAP) or Idle Speed Stepper Motor (IAC) could be bad.It could also be due to a partially clogged fuel injector, low fuel pressure or a vacuum leak. Some testing will have to be done to locate the problem.  

it was doing this before the head gasket.  as in cheap I mean no name station garbage.  the stuff i won't put in my lawnmower.  it happens more when its cold.  

Was the head gasket bad with only 23k? Is it under warranty?  

yeah its still under warranty  

THEN TAKE IT TO A DEALER!!!!!!!!!!!!!!!!!!!!!  

Thanks, for the informative help d bag.  

I dont realy think name calling is needed! Lets see you have a problem with your jeep...i gave you many ideas"The Throttle Position Sensor (TPS), Coolant Temperature Sensor (CTS), Manifold Pressure/Vacuum Sensor (MAP) or Idle Speed Stepper Motor (IAC) could be bad.It could also be due to a partially clogged fuel injector, low fuel pressure or a vacuum leak. Some testing will have to be done to locate the problem."..... its still under warranty...and you wont take it in even though its under warranty?!?! and you wana call me names?!?!!?  

No maybe I took that all cap letters "TAKE IT TO THE DEALER!"wrong?  Now I do appreciate the suggestions   I was just at the dealer and it wasn't fixed, just the head gasket. I don't want to sound like a nancy no engine lights came on.  It just rubbed me the wrong way.  What if my warranty didn't cover one of those just to diagnose cost $.  Simple misunderstanding.  

If its under waranty, go there and tell them to keep it til they fix it. I mean waranty is waranty, the dealers are good about it where i live.