What is a valve mismatch in cars. code 300, 302, 420. All togather. Mechanic is telling the truth to do tune up and all. Is iT valve itsef? What is a (bad) coild? MITSUBISHI MIRAGE 2000
Wherever you are get out. You are about to be ripped off. This will probably be too late. I gather the code you gave is the trouble code, as they are called, from the cars obd. The code 300 is random / multiple cylinder misfire. The code 302 is cylinder # 2 misfire The code 420 is catalytic system below threshold bank # 1 Deciphered this means you have a spark plug misfiring in cylinder #2, bank # 1. The misfire is causing a rich gas mixture in the exhaust system that is detected by the sensor and therefore it says you have a catalytic converter problem. I would suggest you replace your spark plugs, if they have a lot of miles on them. Are they the original plugs ? I f so they are probably due. Get out of there and go find an honest shop that will not rip you off. Now that you know the problem they can;t cheat. I don't know what all that other valve business was about but all you have is a misfiring spark plug.
