Po302, 1999 Jeep Cherokee #2 cylinder misfire

If a tune up (spark plugs, ignition wires, distributor cap/rotor button or coil packs) don't work, try checking the fuel system.

change spark plugs & wires & coil packs to cylinders that are firing & if those cylinders start misfiring it is one of the 3 i do them one at a time if you have a distributor change cap &rotor

Cylinder #2 is the the second spark plug counting from the right to left.
EX.Below are spark plug on engine
engine
-------------------------------
' (oil cap) '
' (4) (3) (2) (1) '
'_________________'

Your misfire can be cause by couple of things but the cheapest way that you can try to fix your car is to do a tune up by replacing:
1)all spark plugs
2)do a oil change
3)spark plug wires
3)distributor cap and rotor

note misfire can be cause by:
1.bad gas
2.spark plug and/or wire
3.distributor cap and/or rotor
4.valve adjustment
5.injector
6.off timing
7.ECM
8.bad wiring(power, ground or feed line)

Most misfires can be corrected with spark plug change. After that you would need to consider distributor cap and rotor ( if it has one) and wire set change. Less common is a faulty injector.

I think it means that the number one cylinder is misfiring, which could be spark plug, coil, the plug wire, or the injector. Usually, if the injector is at fault it will have a code for that. Take the spark plug out and check the condition of the plug. If the plug seems alright, swap it with the number 2 spark plug and clear the trouble codes. If the plug was at fault, the computer should throw a code for cylinder 2, if it still throws a code for cylinder 1, then it may be the coil, If the engine has a distributor, change the distributor cap and rotor.

Well, Spark Plugs wear over time,seldom fail to fire
A worn or dirty rotor and cap will still fire, also

You never throw new wires at it,I don't,mine last 18 years,
on all vehicles

You need some OBD2 knowledge,start studying

The PO302,last # is the cylinder
Number 2 is misfiring

If you got individual coils, go there
If you got an ignition module, for all the cyl,go there
If you got plug wires,there is an extremely odd chance, one burned out inside ,on #2
& you did say your have a dist cap.

So you do have a cylinder monitor,that detected it
That may be the crank sensor,another possible

Need to know the system and how to test it.

You need to give veh specifics ,not just a year

I would manually set it up to top dead center. (Rotate the engine by using a breaker bar and socket on the crankshaft pully bolt the same direction as it runs) with the front cylinder, #1, assuming you have a 4.0 liter straight six, spark plug out. Put your finger in the spark plug hole, and as the engine is turned by hand, you will feel "air pressure." This is coming up onto the compression stroke. With the piston at top, you are at top dead center. (Zero aligned for timing marks) Now remove the distributor cap, your rotor should be pointing at the stud for the number one plug wire.
Turning it will then move the rotor to the next plug to be fired.

301 & 306 are cylinder #1 and #6 misfire. Your spark plug wires are not in the proper firing order in relation to the correct cylinder and distributor locations.

Check and/or replace the easy stuff first. Spark plugs (all), plug wires, Distributor cap and rotor. If these don't solve it have a wet and dry compression test and fuel pressure test done. those tests will get you in the right direction.

good luck

Trouble code P0043 means: HO2S Heater Control Circuit Low (Bank 1, Sensor 3)Hex code 43 is for a misfire.

DTC 43 indicates a cylinder misfire, but does not specify which cylinder is misfiring. To pinpoint which cylinder is misfiring, you need a scan tool and get the "P" code, as you can see in the chart below. So it is quite possible you're barking up the wrong tree.


If you go to an Autozone they will scan the codes for you, if the CEL is currently on, and tell you the DTCs they find. That will get you closer to the problem.
I'm fairly confident that if you do a complete tune-up, spark plugs, spark plug wires, distributor cap and rotor, that the misfire codes will be taken care of. Be sure you read this, Dodge Ram 1500 Running Rough before replacing the spark plug wires, or if you have already replaced them.

Hope this help (remember comment and rated this)..