* Loose or incorrectly installed spark plugs: The most common cause. If a spark plug isn't seated properly or is loose, it can cause a misfire, triggering the light. Double-check that each plug is tightened to the manufacturer's specified torque (you'll need a torque wrench for this – crucial to avoid damaging threads). Over-tightening is just as bad as under-tightening.
* Damaged spark plug threads: If you cross-threaded a plug during installation, you could have damaged the cylinder head threads. This is a serious issue requiring repair.
* Incorrect gap on spark plugs: If the spark plug gap is incorrect (too wide or too narrow), it can cause a misfire. Check the gap with a feeler gauge and adjust if necessary according to the manufacturer's specifications.
* Damaged or faulty spark plug wires (if applicable): While you changed the plugs, check the condition of the wires (if your model uses them, some use coil-on-plug). Look for cracks, fraying, or damage that could interrupt the spark.
* Other underlying engine issue: The spark plug change might have revealed a pre-existing problem. The misfires detected from the faulty plugs might have masked a problem like:
* Bad ignition coil: A faulty coil can't deliver sufficient voltage, leading to misfires even with new spark plugs.
* Faulty oxygen sensor: An O2 sensor malfunction can affect the air/fuel mixture, triggering misfires and illuminating the check engine light.
* Mass airflow sensor (MAF) problem: A faulty MAF sensor provides inaccurate air intake readings, resulting in incorrect fuel delivery and potential misfires.
* Crankshaft position sensor (CKP) issue: A faulty CKP sensor prevents accurate timing of the spark, causing misfires.
What to do:
1. Recheck your work: Carefully examine each spark plug to ensure it's properly seated and tightened to the correct torque. Use a torque wrench.
2. Inspect spark plug wires (if applicable): Check for any damage.
3. Use an OBD-II scanner: Obtain a code reader (available at most auto parts stores). This will give you the specific trouble code(s) stored in the car's computer, providing a more precise indication of the problem.
4. Consult a repair manual: A repair manual specific to your 2004 Dodge Ram will have the torque specifications and other valuable information.
5. If you're not comfortable troubleshooting this yourself, take it to a mechanic: Incorrectly tightened spark plugs can cause significant engine damage.
Without knowing the specific trouble code(s), it's impossible to give a definitive answer. The OBD-II scanner will be your best tool to diagnose the problem.
