2003 Honda Odyssey

Replace the spark plugs and do a valve adjustment.

Adjust the valves only when the engine is cold.
You will need to remove the intake manifold, the six coils and the cylinder head covers.
Then set the No. 1 piston at top dead center (TDC). Align the pointer on the front upper cover with the No. 1 piston TDC mark on the front camshaft pulley.
Use the correct feeler guages:
Intake:
0.20-0.24 mm (0.008-0.009 in.)
Exhaust:
0.28-0.32 mm (0.011-0.013 in.)
Insert the feeler gauge between the adjusting screw and the end of the valve stem and slide it back and forth; you should feel a slight amount of drag.
If you feel too much or too little drag, loosen the locknut and turn the adjusting screw until the drag on the feeler gauge is correct.
Tighten the locknut and recheck the clearance. Repeat the adjustment, if necessary.
When Finished with #1 rotate the crank to #4 and do the same then follow by #2, #5, #3 and #6.