2003 grand am 3.4 code p0304

You may have a wiring problem between the ignition module and the C4 injector (a connector issue at either end or with the the wire itself), or the ignition module may be faulty.

P0113 is Intake Air Temperature Circuit High Input, Internally failed IAT sensor Faulty connection at IAT sensor Open in IAT ground circuit or signal circuit Short to voltage in IAT signal circuit or reference circuit IAT harness and/or wiring routed too close to high-voltage wiring (e.g. alternator, spark plug cables, etc.) Faulty PCM (less likely but not impossible)

P0172 is Fuel Trim System Rich Bank 1, Faulty front heated oxygen sensor
- Ignition misfiring
- Faulty fuel injectors
- Exhaust gas leaks
- Incorrect fuel pressure
- Faulty Mass Air Flow (MAF) sensor

P0304 is Cylinder # 4 Misfire, Known Failure Points:
1. Plugs- specifically Bosch Platinum plugs tend to self-destruct
2. Ignition Control Module- Kinda a "go" or "no-go" type thing. When it fails, you most likely won't be able to start your car.
3. Coil Pack Housing (usually white, some aftermarket are black) - Seems like an unlikely part to go, but from what I hear the plastic can breakdown and cause crossfiring.
4. Coil Pack- Haven't had a bad one yet, but it's entirely possible.
5. Plug Boots- If they're old, they might dry out and crack due to the high heat they are exposed to. Again, not very likely, but when all else fails.

I had the same problem with my ford and replaced the plugs wires and coil packs. that did not fix it so I replaced cam sensor and it solved my problem

Error Code: P0303
Description:
Cylinder 3 - Misfire Detected
Possible Cause:
Wiring harness, igniter and fuel injector connectors.
Ignition system. (Spark plugs gaps)
Fuel injector No. 3.
Fuel pressure.
Running out of fuel.
EVAP canister purge valve.
Evaporative emission system.
Low compression, cylinder No.3. (check valve clearance and throttle plate for excessive wear)
Engine control module (ECM).

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.

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/wires). 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 equipped). Otherwise, check the coil packs. Sometimes the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your catalytic converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.

The page LINK here is the best i have read on misfire diagnosis, it is protected so I can't copy it but you can go to the link.

P0304 is a misfire cyl 4, check the plug wire, and spark plug

The only thing left would be fuel. Check fuel pressure , replace the fuel filter, and check the injectors(ohm's from 11 to 15) and the injector harness. Mostly on the harness make sure you didnt pinch a wire putting it back together, especially the map and coolant wires.

A code P0300 may mean that one or more of the following has happened:
* Faulty spark plugs or wires
* Faulty coil (pack)
* Faulty oxygen sensor(s)
* Faulty fuel injector(s)
* Burned exhaust valve
* Faulty catalytic converter(s)
* Stuck/blocked EGR valve / passages
* Faulty camshaft position sensor
* 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.

Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.

Hope helps (remember to rate this).

Has anyone found the problem? My 2003 has #3 cyclinder misfire and I have replaced the plugs and wires. It runs rough at idle but smooths out at highway speed. Anyone have any knowledge on this? This sounds like a common problem.