Join Date: Oct 2011
Location: Magnetic Hill, New-Brunswick
I think you have a lot of borderline problems causing this DTC to set. Idle speed too low, weak or older battery, dirty throttle body,throttle up signal from "BCM" and possibly your ECM control voltage for cylinder 4. Check battery voltage with engine off, a good battery will read between 12.3 and 12.8, then measure voltage at idle speed after warm-up it should read 14.3 approx.
If changing the plugs and coils did nothing then it must be voltage related and the weakess link is first to set a code ( in this case cylinder 4 )
DTC P0304: Cylinder 4 Misfire Detected
The engine control module (ECM) uses information from the crankshaft position (CKP) sensor in order to determine when an engine misfire is occurring and uses information from the camshaft position (CMP) sensor in order to determine which cylinder is misfiring. By monitoring variations in the crankshaft rotation speed for each cylinder, the ECM is able to detect individual misfire events. If the ECM detects a misfire rate sufficient to cause emission levels to exceed mandated standards, DTC P0300 sets. Under certain driving conditions, a misfire rate can be high enough to cause the 3-way catalytic converter (TWC) to overheat, possibly damaging the converter. The malfunction indicator lamp (MIL) will flash ON and OFF when converter overheating, damaging conditions are present and DTC P0300 is set. DTCs P0304 correspond to cylinders 4. If the ECM is able to determine that a specific cylinder is misfiring, the DTC for that cylinder will set.
Conditions for Running the DTC
• DTCs P0121, P0122, P0123, P0221, P0222, P0223, P0335, P0336, or P0338 are not set.
• The engine speed is between 420-7,000 RPM.
• The engine coolant temperature (ECT) is greater than -30°C (-22°F).
• The fuel level is more than 11 percent.
• The ECM is not in fuel shut-off or decel fuel cut-off mode.
• The ECT is less than 47°C (117°F).
• DTCs, P0304 run continuously when the above conditions are met.
Never drive faster than your guardian angel can fly
Last edited by Coby7; 04-05-2013 at 04:42 AM.