Today, I just replaced the spark plug with the identical ones it came with – NGK IX Iridiums. NOW, the car is making strange sounds at idle at 4500 RPM – what’s wrong? It is a 2008 Honda Accord EX 4 cylinder (46,000 miles).
Generally when this happens, the best course of action is to double check your work. We can all make mistakes or simply overlook something simple.
Spark Plugs
In your case specifically I think the first thing I would do is to remove each spark plug. Check each spark plug gap to make sure one of them isn’t closed. This can happen when they are shipped or moved or dropped accidentally. If the plugs check out OKAY, them install. Another thing to check, as far as the spark plugs are concerned, would be to see if they are arching externally. This can happen if the porcelain is cracked(cracked insulator) or a plug wire boot is cracked. It will allow spark against the cylinder head and seem like an engine misfire.
Do not adjust gap of iridium spark plug. Replace spark plug if gap is out of specification.
- Adjust gap of non-iridium plug to .039-.043 inch.
- Torque spark plugs to 13 ft. lbs.
- Inspect spark plug removed from cylinder head.
- Burned spark plug electrodes may be caused by ignition timing that is too advanced, a loose spark plug, a plug with too hot of a heat range, or insufficient engine cooling.
- Fouled plugs may be caused by excessively retarded ignition timing, oil in combustion chamber, incorrect plug gap, a plug with too cold of a heat range, excessive idling or low speed operation, clogged air cleaner element, or deteriorated ignition coils.
Connections/Vacuum Leak
The next thing to check would be any and all electrical connections that you may have unplugged during your work. Also you will want to make sure that any hose clamps or air intake hoses are installed correctly. Leaving one loose or disconnected will change the engines ability to perform correctly. This can cause a vacuum leak and throw off the sensor readings.