My 99 jeep grand Cherokee will **** and cut off after driving it 30 minutes or so. I had the motor replaced and the coil pack. Like I said it will run and start fine but will **** after awhile then I was told alittle smoke come from tail pipe and then cuts off. Running out of options and money any suggestions?

The 6 cyl engine uses a coil strip for all 6 cylinders, and the 8 cyl uses one coil per cylinder. So I assume you have an 8 cyl engine.
You are saying one coil has power but is not firing ?
Have you switched it with another cylinder to eliminate the coil as a possible problem ?

Assuming you are going to replace the 99/04 Jeep Grand Cherokee blend doors yourself.
You would start by disconnecting the negative battery cable.
If you are going to remove the dashboard, etc to replace the blend doors.
some websites give you complete instructions with plenty of pictures.
It will take the average person with little or no auto repair skills approximately 12 to 16 hrs.
The vehicle will have to be taken to a shop that can recover the refrigerant before you start removing the dashboard and HVAC box..

If you are going to do the type of repair where you cut an access hole in the side of the HVAC box.

A short version of how the access hole repair is done.

Disconnect the Negative battery cable.

Lower the glove box

Remove the actuator motor - You will need a Phillips screw driver

Cut an access hole in the plastic HVAC box - Use a multi-purpose cutting bit, you will need a rotary type of cutting tool, like a Dremel, RotoZip, etc. Or you could do the cutting by hand with any type of small cutting tool, it will just take longer doing it by hand. Or some people have used a narrow pointed soldering iron!

Remove the broken blend doors

Install the new blend doors.

Replace the actuator motor.

Close the access hole - Replace the wall piece of plastic you cutout -Use foam tape or an aluminum tape to cover the groove made by cutting the wall.

Close the glove box.

It is almost as easy as what you just read, the hardest and the most time consuming thing to do is cut the access hole.
The job should take between 30 minutes to 1 ½ hours. Depending on how long it takes you to gather your tools, etc.

it does sound like the ecu is bad the only other thing it could be is the antitheft system is having problems

TO REPLACE SPARK PLUGS YOU REMOVE COIL PACK MOUNTING BOLTS THEN REMOVE THE COIL PACK WITH BOOT OVER THE SPARK PLUG.YOU HAVE 6 INDIVIDUAL COIL PACK TO EACH CYLINDER. YOU NEED A 3/8 RATCHET WRENCH - LONG 3/8 EXTENSION -SPARK PLUG SOCKET - SPARK PLUG GAUGE.AND TORQUE WRENCH.THE 2000 MODEL JEEPS FUEL FILTER INSIDE THE TANK.1993 - 1996 MODEL JEEPS FUEL FILTER LOCATED LEFT SIDE OF THE VECHICLE NEAR THE FUEL TANK.

If it is a 4.0L, remove the 4 13mm bolts and lift up on the coil pack and flip it over. Remove your spark plugs and install the new ones. Put dielectric silicone in the boots and reinstall the coil pack. If it is a 4.7L, you have to remove the air box on the top of the engine. Each cylinder has it's own coil pack which is retained by a 10mm nut. remove this and the coil pack comes out. the 2 rear on the passenger side are harder to remove because of the transmission dipstick bracket. You will need a long extension to get the spark plugs out. Repeat the same procedure from the 4.0L installation. Hope this helps

Best of luck

possible fuel pump

Sounds like you both are having problems with your coil packs.  When they start to go bad and get hot, they will shut down on you for a while until they cool back down enough to start working again.  They will get progressively worse as time goes on.  I believe that you can take the coil packs to AutoZone and have them tested for free.  Let me know if you have any other questions, but I think this will take care of you both.  Thanks for rating my response and for using FixYa!

Sounds like the actuator went out. There normally run 40-60 for the part and does not take long to replace normally 30 minutes.

You say you changed the cam sensor. A1391 code is a crank sensor on the top of the trans. bell housing.

It could very well be the MAP sensor. I believe it is on the fire wall of the '99s . unplug it and see if thet doesn't help. If it does, then replace the sensor. (MAP sensor will have a vacuume hose and a small plug in attached).

The mass airflow meter could be the culprit as well.

Are you getting any codes?