I have these failure codes on a 1998 camry. It has very low power but idles fairly smooth. Timing belt and plug wires have less than 50k miles & all plugs (just changed) seem to have good spark. Vacuum gauge shows a steady 18 lbs. What is throwing me is the fact #4 cyl is not showing a misfire. Any help will be appreciated.

P0300--Random Misfire
P0301--Misfire Cyl. 1 Or Random Misfire
P0302--Misfire Cyl. 2 Or Random Misfire
P0303--Misfire Cyl. 3 Or Random Misfire

. Ensure you are using the same NGK single platinum plugs that originally came in the car, gapping plugs to spec. (.044 inch). Lightly coat the porcelein portion of the plug and electrode with dielectric grease.

. Wipe spark plug wires down with a cloth and silicone spray.

. Replace coil, if the problem persists. Use dielectric grease on all connections.