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P0304 is engine misfire #4 cylinder Several things can cause a misfire #1 electrical which you have covered #2 Mechanical Test engine compression is should be around 150 cranking and 120 running . internal valve train components can cause bad compression and the valves then self. #3 fuel injector can be the cause suggest swapping with a know good cylinder and see if misfire follows injector.
P0304 Cylinder 4 Misfire Detected,A code P0304 may mean that one or more of the following has happened:
Faulty spark plug or wire
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector
Burned exhaust valve
Faulty catalytic converter(s)
Running out of fuel
If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs).. I would suggest spark plugs, sparkplugwires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced.
P0304 Code - Cylinder #4 Misfire Detected A P0304 code means that the the car's computer has detected that one of the engine's cylinders is not firing properly. In this case it's cylinder #4.
Symptoms may include: * the engine may be harder to start * the engine may stumble / stumble, and/or hesitate * other symptoms may also be present
Causes: A code P0304 may mean that one or more of the following has happened: * Faulty spark plug or wire * Faulty coil (pack) * Faulty oxygen sensor(s) * Faulty fuel injector * Burned exhaust valve * Faulty catalytic converter(s) * Running out of fuel * Poor compression * Defective computer
Possible Solutions: If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.
If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.
See if you can get the codes. If it is still number 4 only (probably a P0304) it could be the fuel flow through injector 4. Try some Techron cleaner and make sure number 4 plug isn't fouled. Also get the compression checked on number 4.
If not, it could be the ignition control module assuming all other changes have been made. If you get a code it will help. A P0300 would point toward the ICM. If it is number 4 only it could still be the ICM. Expect around $150 for the module if you do it yourself. The ICM may be under the coil pack. If you are getting a P1361 and/or P1362 it could be the Cam position sensor. They are around $40 and are usually near the number one cylinder. Mine is hiding under the water pump pulley. It is a Buick with the 3.8 engine but the principal is the same.
A P0304 OBD2 code is "cylinder #4 misfire detected". The first place to start is your spark plugs. 1. Check condition and for wear. 2. check the spark plug wires or coil packs(depending on which you have).
I also have the same problem with my 2002 caravan 3.3L. Misfire on cylinder #5 (P0305). Replaced ignition plugs & wires, intake manifold gasket, plenum gasket, fuel filter, air filter, cleaned fuel injectors, swapped fuel injector #5 to #1. After all these, I have no more DTC code but the symptom of misfire is still there, the idle is rough and I can feel the misfire even if I step on the gas when in park or neutral. Please let me know what to do next. Thanks!