I have a 2005 Toyota camry 4 cylinder 2.5 2AZ-FE engine with 137,000 miles. I’m the third owner and it was initially owned by enterprise rental cars. I bought it at 100,000 miles from used car lot.

It had a check engine light with PO351 and PO353 codes. The car also vibrates occasionally on the driver side all of sudden and it goes away when I turn off the engine and start it after 10 minutes or so. Two of the old spark plugs and one ignition coil were coated with oil, when I changed all the four spark plugs with Denso Iridium spark plugs and Denso ignition coils and reset the check engine light. My car still vibrates occasionally. The car is running smoothly after the spark plugs and ignition coils replacement. The check engine light still comes back on with PO351 code. I still cannot figure out the cause for vibration and the PO351 code coming back.

Appreciate your Help in advance.

Note: I drive only 5000 miles a year and intent to keep it for another two years.

Is it worth changing the sparkplug tubes and valve cover gasket?