dumpsterdom89

Hi. I have a 99 grand cherokee Laredo with the 4.0. I got it with 92K and now have 170K. Apparently, the vehicle sat, undriven, for two years. The only maintenance that has ever been performed on it in the past five years that I've owned it include: tail light replaced, exhaust(x2), brake rotars and pads(x3), fuel filter. Obviously, I have changed the oil and replaced the air filter. I did replace the plugs the first fall I owned it without replacing the wires....I plan on changing both this month. Also, O2 sensor is bad, causing my "check engine" light to be on all of the time.
Ok. Now that you have some background info... ever since I've had this thing, it acts funny within the first minutes of being started. If it is started and allowed to sit and idle, most times the engine shutters and sounds like it wants to stall out. Feeding it throttle while idling makes it worse once you let it idle again. If I begin driving instantly after starting- it takes off in lower rpms fine (going down the driveway). When I accelerate, the engine hesitates. I can briefly put the peddle to the floor with no response. If I keep applying gas through the hesitation, the motor pops and accelerates jerkily. After doing this once or twice, on average, the engine runs totally fine. I find that "feathering" the gas helps correct the problem, sometimes without the "popping" ever occurring. I have put some stupid hard miles on this thing and I break almost everything I own. This engine must be bulletproof. I feel like I should have tried to solve this problem along time ago to reduce wear and tear on a vehicle that needs to last me.

Here are my thoughts on the problem. (1)The o2 sensor is sending bad info to the computer-causing the wrong mixture to be used while the engine is cold leading to the hesitation and miss-fires . (2) This engine was designed to run on higher quality gas than is being produced today (though I never use low octane). (3) plugs and wires need to be changed. (4) dirty fuel injectors and throttle body. (5) combination of all mentioned plus others.

Any input on this would be greatly appreciated. Drive safely.

Dumpsterdom89

Zj heep

Sounds like you know what your problem already is. A bad o2 sensor and dirty tb can cause that. Run some fuel additive with your next fill up it should help. Good luck.