My 1994 Jeep Grand Cherokee Loredo 4.0 4X4 idles very roughly and is difficult to restart when warm. History: I replaced the plugs, distributor cap, rotor, plug wires, Idle air Valve, Fuel Pump, fuel filter, Cleaned throttle body, Cursed profusely. I drove 680 miles last week from Florida to NC and it ran just fine but still idled pretty rough. The morning after the drive in 34 degree weather the car would not start. The starter turned the engine over rapidly but it would not start. I had it hauled into the local dealer who said the fuel pump was bad. He replaced the pump and the Jeep started just fine but idled even more roughly than it had before. With the new fuel pump and filter it starts fine when cold but is hard to start when the engine has been running for a while is shut down and then re-started. I just drove the vehicle from NC to Florida and left it running during fuel stops because of difficulty in starting. It ran fine except for rough idle and difficult warm starting. At an average speed of 70 mph it got 20 mpg using premium fuel. Help!!!!!!

what engine (4.0L or 5.2L)?
Have you checked the FUEL PRESSURE (sounds like YOu Fuel Pressure might be low)?

Could be a bad CPS, they tend to become sensative to heat after awhile (seeing that they are mounted on the engine block).

When it is difficult to re-start, have you checked for SPARK, Fuel Pump kicking on and does the CHECK ENGINE light come on, when attempting to restart?

Like 81 said try the CPS also the Cam or Halls efect sensor can do the same thing. The next time check for spark and fuel pressure. On the rough Idle check for vacuum leaks and make sure your egr valve is operating.

For 81 & Cam7: I checked the codes and get 34 & 55. It is a 4.0 engine and has a new fuel pump and filter. I'll check the egr and the check engine light.
Thanks

What and where is the EGR valve and how can I check it? Thanks

I have a 93 grand cherokee 4.0 with the exact same problem. In fact I have had it for almost 2 years now. I and the dealership have replaced every sensor there is under the hood with no help at all. I have also replaced the computer, distributor, coil, and multiple other parts with no difference. It is not a fuel pressure problem as my fuel pump, filter, and regulator have all been replaced and pressure checked multiple times. If you think about it if it were a fuel problem it would be hard to start after sitting for a while. Mine is hard to start after it has been driven for a while, gets to a operating temp. then if you shut it off for 5 minutes or so it is hard to start. However if you let it sit until it cools off it starts right up. I have come to the conclusion that it will never be fixed, lol. I wish you good luck, but don't fall into the "I'll get this fixed no matter what" syndrome I fell into, way too expensive, lol.

I have a 93 grand cherokee 4.0 with the exact same problem. In fact I have had it for almost 2 years now. I and the dealership have replaced every sensor there is under the hood with no help at all. I have also replaced the computer, distributor, coil, and multiple other parts with no difference. It is not a fuel pressure problem as my fuel pump, filter, and regulator have all been replaced and pressure checked multiple times. If you think about it if it were a fuel problem it would be hard to start after sitting for a while. Mine is hard to start after it has been driven for a while, gets to a operating temp. then if you shut it off for 5 minutes or so it is hard to start. However if you let it sit until it cools off it starts right up. I have come to the conclusion that it will never be fixed, lol. I wish you good luck, but don't fall into the "I'll get this fixed no matter what" syndrome I fell into, way too expensive, lol.


Bluegoat,
My 1994 does exactly the same thing. It starts great when cold and very difficult to start when warmed up. This thing is rapidly reaching the point of diminishing returns. Toyota and Nissan are starting to look real good.
LELeach