I have a 99 Jimmy with 4.3 engine. I have bad missing in the engine. I have replaced all wires, plugs, cap and rotor. This unit is still missing and setting a general misfire code. I have no vacuum leaks either. What is up with these systems? No problem starting it, it will start right up. Can't seem to pinpoint the problem.

check for spark at the plugs then check for fuel. if one of these are missing the car won`t start. common problem on some of these was the ignition module in the distributor and sometimes the pickup coil wires would break. another thing to check is the distributor cap and rotor for damage like a cracked cap or burnt through rotor. fuel pump were also common.

the problem is not in the plugs , wires , cap , rotor but in dirty injectors or injector controls and wires
use a quality injector cleaner for a few tanks of fuel
ECM controlled cars do not a tune up as the computer does that 60 times a minute so all you need to do is to run the fault codes and fix the faulty sensors
fault codes are being recorded all the time and only the serious engine or transmission faults put the engine light on

engine missing could be caused by faulty spark plugs and wires,bad ignition coils,dirty fuel injectors,leaking egr valve,low cylinder compression,intake vacuum leaks.many things will cause engine to miss, first do minor fix,replace distributor cap and rotor,replace spark plugs and wires,clean fuel injectors,replace fuel filter and air filter,if this minor tune up dont help engine and engine still missing, do a vacuum test and compression test to check condition of engine.engine could be worn out have low compression by worn valves and pistons rings.

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)

depending on what motor is in your Jimmy and if it still has a distributor, that is where i would start. moisture will get in side the distributor and cause a miss fire. This is a common problem with GM trucks that still have distributors instead of coil packs. Try haveing some one replace the cap and rotor or silicone around the cap and see if it seals.

Change the fuel filter

Please help us. I have the same problem with my 99 Jimmy. I was driving on the highway going 70 and then it started missing. Changed all the plugs, wires, rotor and cap but to no avail. HeLP! please email me if you have a solution to this problem. ([email protected]) thanks a bunch.

If it jumped time it may backfire and run poor but not miss.
Check coils and wiring.

replace the cap and rotor with gm parts or you will still have an issue

Aloha We have just replaced all of what you have replaced, plus water pump, fuel pump, pcv valve and 02 sensor. Took it to mechanic today we had misfire on 1,2,6,7. Mechanic said that the 99 dodge is known for bad computers, he checked ours and works great turns out that it was the coil. Ours was jumping 1/4 inch and had a orange/yellow spark. it is supposed to have a 1 inch spark and be blue. This has solved our problems after 527 dollars later.
Check the coil!