Valve Clearance Adjustment on 2003 – 2007 Accord
This is the procedure for a valve clearance check/adjustment on the 4cyl. 7th generation i.e. 2003 – 2007 Honda Accord. As per the owners manual, this procedure is recommended every 110,000 miles or if the valves become noisy. Intake valves let the air-fuel mix into the combustion chambers whilst the exhaust valves vent the burnt gases into the exhaust system. It’s widely said that exhaust valves tighten while the intake ones loosen over time (for solid valves though). The valve clearance for this model is:
Intake: 0.21mm – 0.25mm (0.008inch – 0.010inch)
Exhaust: 0.28mm – 0.32mm (0.011inch – 0.013inch)
Feeler gauges; curved feelers gauges are better (I used; intake-0.22mm, exhaust-0.30mm), torque wrench, 10mm jam nut tool (recommended but a 10mm ring spanner & flat screwdriver will do. The jam nut tool makes the process easier), 19mm socket, wrench & extension, and 16mm spark plug socket.
NB: The firing order for this engine is 1-3-4-2 and as such, the valve clearance check/adjustment will follow this order. Cylinder 1 is the one closest to the power steering pump.
Valve clearance check and adjustment should only be done on this model with the engine temperature at 38°C or less. Best done first thing in the morning!
1. Remove the front right wheel: This is to gain access to the 19mm crankshaft bolt that would be turned to achieve top-dead-centre (TDC) position for the different pistons. Attach the 19mm socket to the crankshaft bolt but do not turn.
2. Remove the negative battery terminal: For safety purposes.
3. Remove the valve cover: The steps for this have been covered in this previous post; Valve cover gasket replacement on 2003 -2007 Accord
4. Remove the spark plugs: Remove using the 16 mm spark plug socket and set aside. I usually keep the plugs such that I know which one came out of which cylinder.
Above is an image showing the exhaust and intake camshafts and their respective sprockets. The red circle also shows the locking screw which overlies the valve lash.
5. Check and adjust valve clearance: valve clearance check and adjustment should only be done at TDC positions. Set the piston in cylinder 1 to TDC (TDC is the position of the piston at which it is farthest from the crankshaft). To do this, there are punch marks and TDC dashes on both intake and exhaust camshaft sprockets. The punch marks on this model are highlighted by Honda in orange ink. At TDC the punch marks and TDC dashes would be at certain distinctly related positions. By turning the crankshaft bolt clockwise the exhaust and intake camshaft sprockets will turn clockwise as well to achieve a TDC position. A 180° degree turn of the crankshaft will turn each sprocket 90º.
At TDC in cylinder 1, the TDC dashes on the sprockets will be aligned to each other i.e. exhaust TDC dash will be at 3 o’clock position while that on the intake sprocket will be at 9 o’clock position. Both punch marks will be at 12 o’clock position. Because of the ABS lines and pump are in the way, getting pictures of the TDC marks is difficult. However, I produced a diagram showing the positions of the both marks at TDC on the different cylinders.
So to achieve TDC on cylinder 1, turn the crankshaft clockwise until the marks on the sprockets align to those shown above for cylinder 1. Then check the valve clearance at the intake valves using the set feeler gauge.
If the valve clearance or lash is out of spec, use the jam nut tool to slightly loosen the locknut and with the included flat screwdriver loosen or tighten the adjusting screw accordingly. Tighten the locknut and then recheck the clearance to ensure it is within spec. Torque for locknut is: intake – 20Nm & exhaust 14Nm.
After this do same for the exhaust valves with the right feeler gauge. Next, turn the crankshaft bolt 180° clockwise to attain TDC on cylinder 3 (Refer to position of TDC marks for cylinder 3 in the diagram above). Check and adjust valve clearances if necessary. Turn the crankshaft another 180° for TDC on cylinder 4 and after doing the needful, turn the crankshaft another 180° for TDC at cylinder 2.
In the end, the valves needing adjustment on mine were intake valves on cylinders 1 and 3 and the exhaust valves on cylinder 2.
All said and done, replace the valve cover replacing the valve cover gasket if worn. The steps for this can be found here. Cheers!