I have had my 2000 Jeep Cherokee Sport, 4x4 4.0 6 cylinder automatic, for quite some time now and it has 103,000 miles on it. Most recently I ran into a problem. When my Jeep has been sitting outside in the cold for a while and I go to start it up in the morning, it shakes profusely for a good few seconds. Then, when I start to drive sometimes it will stall almost as if my Jeep won't allow me to drive. I push down on the gas as far as it will go and it won't go. After a few seconds of that, the Jeep will finally go back to normal and drive fine. This happens a few times during the course of the day and ALWAYS when it has been sitting in the COLD. I have never noticed this happen in WARM weather. I had it taken to an auto shop and the mechanic did a tuneup (replaced all 6 spark plugs), it was fine for about a week and then it went back to doing the same thing. I took it back to the auto shop and he told me my ignition coil pack was bad. He replaced the coil pack with a brand new one, and that also only worked for about a week until it went back to its old ways. Today, I bought 2 bottles of injector cleaner and threw that in my gas tank to see if that would do anything. Of course not!! The engine light is on and when you run a diagnostic, it says there is a misfire in all cylinders. What is the problem and how do I fix this??? It's driving me crazy!!!!!

 

What is the exact code?

 

And is that the only code it is throwing?

 

I wish I still had the printed papers for the codes. From what I can remember it was a misfire in the cylinders.

 

Yes a misfire is the only codes that are coming up

 

Sounds like the fuel pump.

Sounds like you need to find a real mechanic. Not just one that throws parts and your money at it, hoping to fix it.

 

Truth be told. But I would like to identify what the problem is so that a mechanic doesn't just throw my money into useless crap.

 

Take it back to the parts store and make sure to write down the code it is popping up with. I believe there are a couple that have to do with cylinder misfire so the exact code would be very helpful.

 

I took your advice and just went back to the shop to get another diagnostic and wrote down the codes. I am getting 2 different codes. The first says, Definition: Cylinder Misfire Detected- random cylinders
Explanation: The powertrain control module monitors the crankshaft speed and has detected a misfire condition.
Probable Cause: Ignition system fault-spark plug(s), ignition wires, coil
Vacuum leak
Injector Fault
High or Low Fuel Pressure

The second code reads, Definition: Small leak detected. Explanation: The ECM has detected a large leak in the EVAP system during a system monitor test. Probable Cause: Defective, loose or missing fuel cap
EVAP canister broke, hose cracked or not connected
Purge or vent solenoid defective
Vacuum leak at engine

I hope you guys can tell me what my problem is now!! Thank You!!

 

These codes don't have numbers? Like p0122 or p1391? something of that nature. Yeah the explanation can give you the idea but the actual code number is what you need.

The leak could be any of those things listed. Check your evap canisters for holes or loose lines. As for the vacuum leak possibility, do you hear any high pitched whistling or something similar when you are driving it?

 

On another note have you looked at your crank position sensor yet? When those go bad it can cause it to run very badly. And if it goes out completely it wont even start. You can test it with a multimeter to see if its bad.

All the sensor is is like a hall effect pickup that detects the teeth on the flywheel as they pass by it. If its going bad its just guessing when to send fuel for spark, which in turn, causes misfire.

Also, I would say the pick-up coil but you have a 2000 and it doesnt have an actual distributor.

 

I had the same problem with mine and it turned out to be the cps I replaced it with a mopar one from the dealer solved my issues with the misfires