It's a jeep thing and I don't understand

[mrrandyz]

My '01 cherokee runs fine under normal driving conditions, but when I use it on my mail route it barely runs when I start it after it's hot. I have to rev the engine to get it to run right again. The MIL came on and it gave a multiple missfire code and some other individual cylinder missfire codes. I also noticed that when starting it this winter, somtimes when starting it when cold it acted like the firing order was wrong. I would appreciate any suggestions. Here's what I've done so far:
Changed the spark plugs, checked the coil rail with an ohm meter (checked out alright), put insulation over the injectors (for the known vapor lock issue), ran valve cleaner through it twice, changed the throttle position senser, cleaned the throttle body... again this only happens on the mail route, when it has reached operating temperature. Thanks ahead of time!

[Airjer_]

my first thought is to check fuel pressure. If its not holding pressure after a hot soak the fuel will boil in the rail and essentially give you vapor lock. Extended cranks after hot soaks usually go hand in hand with dropping fuel pressure.

[mrrandyz]

Thanks for your suggestion I'll have to look into that, but it's not that it cranks extra long; it just starts and then acts like it doesn't want to keep on running until I rev it and it backfires a few times and stutters around before it clears up.

[nova73noir]

first inspect your sparkplugs wire sometimes they look good but are bad,for back fire problem im sure the bank 2 o2 sensor are bad but first change your wire

[FRENCHHILLGILL]

1999 to 2001 4.0 heads with casting number 0331 stamped on top of the head between number 3 cylinder and throttle body are prone to cracking.check your coolant bottle to see if it is draining into the enging oil,oil will be milky.this wipes out the cam bearings.there are also sticking exhaust valve issues with several year 4.0's that may be resolved by spraying mopar combustion chamber cleaner (part # 04318001ab)into the throttle body with the engine running. Follow the directions and don't spray it in too fast oR you can cause a hydro lock where a cylinder gets full of the cleaner and bends a connecting rod.change the oil right after starting it back up.my friend spun a bearing in his toyota 4 x 4 after using this. He only drove 3 miles without changing his oil.chrysler mechanics swear by this stuff.it did a great job on my 89 camery and 89 john deer. Didn't help my jeep a bit. Went to a u-pull-it junk yard and got a 98 head which are supposed to flow the best.it's at the machine shop now getting a valve job.2002 AND NEWER 0331 HEADS WERE CAST IN BRAZIL AND ARE SUPPOSED TO BETTER.GOOD LUCK.Frenchhillbill.