Having problems with your 2006 Hummer H3 ?

Error code reads #4 cylinder misfire??? possible probs & fixes

Posted / edited by AnonymousUser on : 20-11-2017

Answers :

I'm assuming your trouble code is P0304 and you have the 5 cylinder engine.
\015\012take out the spark plug, does it look normal? No foreign materials on it, like coolant or oil? If it has coolant on it, you have a blown head gasket.
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\015\012If plug looks ok, put the wire back on the end of it, pull the wires off the other plugs, hold the #4 plug with wire up against the engine to ground the plug threads. Have someone crank the engine while you look for a spark. If no spark, try putting the plug into another wire. If still no spark, plug is bad. If it sparks in another wire, wire #4 or coil #4 is bad. In this last case, you can swap wires with another coil to determine if it's the wire or the coil that is bad.
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\015\012If #4 plug sparked in wire #4, ignition is working and problem is with the cylinder. Run a compression test on all cylinders. You can borrow or rent the tester. Take all plugs out and screw the tester into each plug hole one at a time. Crank the engine a few revolutions and read the gage. Write down the pressure, release it from the gage and go on to the next cylinder. If #4 comes up short, you have a burned exhaust valve or blown head gasket.
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\015\012Please let me know if you have any questions or need more instructions.
Repair Help & Product Troubleshooting for 2006 Hummer H3

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