msifire
 

so to start things off i got a 2000 jeep cherokee sport 4.0 a few weeks ago . when i got the jeep it had a misfire i was told it needed a coil pack no big deal......well i have replaced the coil pack replaced the crankshaft position sensor with a mopar brand and i replaced all the spark plugs. nothing has helped its still missing is cylinder 2 and 3 codes p0300,p0302,p0303 im lost can anyone lend a suggestion ? also its not burning oil or coolent and it has still has plenty of power

Might want to verify that the injectors are all working. If you have a mechanic's stethoscope you can listen to the injector with the motor running. you should be able to hear a tick tick tick sound.

What are the circumstances when the misfire codes happen? What kind of plugs were you running before and now? Do you have the heat shield on top of your intake manifold still? Bought an '00 a couple years ago. Have been fixing it up. Read alot about misfires. Never had that problem so when I got around to replacing the plugs I put the exact same plug in. Cheap Champions. 438's. Any chance the misfire codes come up after you get the Jeep hot, park it for about 15 minutes, and when you restart it runs rough for a second or two? This could be a heat soak issue. Especially if you do not have that heat shield anymore. Heat in the engine compartment when sitting vaporizes the fuel in the injectors and/or fuel rail. Would not surprise me if the misfire codes are coming up when the Jeep is stumbling for that couple seconds on restart.

If you wanna know a little trick you can take a short piece of wood and put one end on the injector and the other on your ear, you'll be able to hear the tick through the wood.

Yep, I used to use the stick/screwdriver to the ear trick. A mechanics stethoscope is handy because you can use it to hear vacuum leaks too

Start the engine with the hood up in the dark and look at the plug wire... see if you see the spark jumping to the engine block through a bad plug wire or boot. Or maybe something wrong with the plug itself.

i have checked all the injectors they all seem fine and all the plugs and stuff are new im lost im taking it to my local auto shop today.. thanks for the replys everyone

2000 with a 4.0? Isn't that the one with the "0331" head? If it ever got overheated by the PO then the head/gasket may be in-trouble. You might want to check oil and coolant for mixing, and to run compression tests. Sounds unrelated to misfires, I know, but weird stuff happens.

yea i did not check the compression i know i should have but i just dropped it off at the mechanics .. im not sure what head it has im not that mechanicly inclined lol

well the shop checked the compression it was decent they checked the 4 problem cylinders compression was 120 in each they found a broken ground wire on the block and none gaped spark plugs all fixed now!

Yes, those none gaped spark plugs will do it every time.

but you know what i still get a heat soak issue on number 3