Toyota Repair: Burned exhaust valves on a 2001 Prizm, excessive oil consumption, 2001 chevy prizm

Question
Ted,

I have a 2001 Chevy Prizm, which from what I understand, uses the same engine as a 2001 Toyota Corolla. It began using oil at 30,000 and by 130,000 was using so much oil I had a remanufactured engine (Jasper’s) installed. That motor had the variable valve timing cam gear fail at 70,000 miles, under warranty. The engine now has 90,000 on it and has 2 burned exhaust valves (warranty expired). I am in the process of having the head work done, but I would like to prevent the new valves from burning. Before I stared getting misfire codes 300, 302 and 304 due to the valves, the only problem I experienced was the failed cam gear (which only made noise for a couple of minutes after being started hot) and a 420 converter efficiency code. I’ve been told that the excessive oil consumption possibly ruined the converter. Is it possible that a clogged converter or a bad O2 sensor, due to the oil usage, caused the valves to burn? I don’t want them to burn again, but I don’t want to throw expensive parts at the car for no reason. The new engine always had good power and acceleration and got anywhere from 28 to 33 mile per gallon until the valve problem. Additionally, I cleaned the MAF and the throttle body with oxygen sensor safe sprays, replaced the PCV valve, plugs and injectors, all before checking and finding low compression in cylinders 2 and 4. Thank you in advance for any advice you can give about prolonging the life of my valves.

Curt  

Answer
No, the oil usage would not cause the valves to burn, valves normally do this because the valve clearance is too tight, the valve clearance should be checked and adjusted as needed every 60,000 miles. Excessive oil depposits can affect the cat converter but I would not replace it just yet, clear the trouble codes afte rthe vlave job and see if the po420 code comes back after driving for a while.