2004 grand cherokee 4.0l one day it will run fine the next day it runs rough rich and when i step on the gas the engine cuts out and spits and sputters

go to repair shop urgently before its too late............

If the start and run fine are on cold starts, I would look for vacuum leaks. The normal start mode for these things is to have a richer condition upon a cold start. When the ECU detects warmth in the engine is drops the extra rich cold start mode then the idle goes rough due to the normal mixture being too lean due to a vacuum leak. Look for cracked, loose or broken vacuum hoses. It could also be due to a EGR valve stuck open.

what engine.
hot or cold engine , or both?
does the cut out catch up.?
does it have full engine power up a hill wide open throttle. (key test)
on cuts, out tip-in throttle ?
dash CEL lamp off running.
scan PCM , no DTCs stored? (errors)
ever do the 60k mile tune up , (sparks and filters?)
i have 10 more quesitons, id see in 5min testing car. but .... here are some.

it is your air idle control valve witch is located on the back of the throttle body..

go to autozone or pepboys to have the engine light codes pulled. they will give you a print out of the codes, their potential causes and possible solutions.

when was the last time you gave it a tune up that is what is needing

fuel pressure seems a bit high...could be a bad regulator. can't remember if yours is on top of the sending unit (on tank) or on the fuel rail though. Do more testing there.

it looks like your engine is having an over rich fuel mixture maybe, thatswhy when you press the pedal to the floor it starts becouse you allow lots of air to help clean the mixture while cranking, also you should have black smoke in the tailpipe until it cleans up and runs fine, i think youre having a leak in one our more injectors you should check them first for proper seal under pressure these is done in an injector test machine, second it may be a defective map sensor these trucks some times have a bad map and dont give a MIL (malfunction indacator lamp) and last but more rare to be is a blocked fuel pressure regulator chek fuel pressure it should be between 38 and 45 psi and it shoul hold these pressure when you turn off the engine if pressure drops fast its injector seal problems or fuel pump check

A slight hesitation after engine shut off due to engine running rich meaning not meeting golden air:gas ratio of 14.6:1 so fuel residue in chamber continue to burn for the last moment. The same rich fuel problem that was why you had to let gas off during acceleration. Need to Check out the O2 sensor Check out MAP sensor Good luck

I have the same problem on my 95 grand cherokee laredo. Sometimes it starts out fine and after about 10 miles it starts spitting and sputtering. Then after a while it seems to clean out and run fine again for a little while. Then other times it starts out spitting and sputtering at the begining. I changed the fuel filter and that was not it. It is a 4.0L 6cyc. Any Ideas?

Thanks,
Broken Arrow, OK