hi this jim, i,m here to help you out, i am assuming the valves were replaced because they were burnt, burnt valves are usually casued by a lean engine condition, and if the engine is lean the combustion gets very hot and burns the valve and if the valves are too hot the converter gets too hot also and loses its efficiency and then cuase p0420, this code is cut and dry, the computer knows when it stops working, does this make any sense
I am not sure I understand. Are you saying that the hot cat converter caused the valve to fail?
no the other way around, the lean fuel condition caused the valve to burn and inturn the converter got too hot and failed also
Ok, so if I had valve 4 repaired and all of the other parts like gaskets and spark plugs and timing belt, etc... and I drive away and 300 miles later valve 1 fails, is it the car or the mechanic
I am broke now fixing this car and after spending 3k I thought I could get another 50-80K miles out of it
this sounds like the mechanic, he might have the valves in cylinder 1 either too loose or too tight, either condition will cause a misfire code
so you are saying that normally if you have all of this work done and then there is a failure with another valve it would be because of something the mechanic did and not your normal valve failure situation
i hoped he checked all the other valves when he had the head off, that is just common sense, he probably has the valves misadjusted
When I first spoke to him he told me that Valve 1,2, 3 had good compression and valve 4 had almost no compression and was burned up. He sent the head to a machine shop to check for cracks - that cost me $350.
that is good he did have them checked, the other valves are probably ok, i would go back and have him recheck the adjusment first, this should not cost you anything he better stand behind his work, i know i would
Thanks Jim, What is your opinion about driving around with the engine light on and catalytic converter trouble code... He said it would "fix itself in 500 miles" does this sound reasonable?
unfortunately it isn't going to fix itself, once the converter is worn out it is worn out, you don't want to be driving with a msifire condition either, that could damage other things, the computer will try to compensate and make the other cylinders not run right
I won't drive on the misfire code. I will get the car to him first thing in the morning.
There was not a problem with the convertor until we were 5 miles away from the autoshop, I mean this was not a problem before the valve problem. with a CNG car how important is the Cat convertor?
it is important, cng cars have emissions just like gasoline cars, gotta protect the ozone layer, the reason the cat failure showed is probaly because cylinder 4 was operating like it was supposed to
I got you on the ozone layer... so is it possible that if the valves are adjusted properly that the Cat Converter warning will go away?
probably not, the converter will need replaced, i know that is not the answer you want hear, maybe you could split the cost with the shop but you can always see what happens too, driving around with anly a converter good isn;t that bad, but if there are emissions tests where you live the light will have to be off, i'm guessing you live in california
Ok Jim, any other words of advice for me when I go to the shop tomorrow with my car... what I should say to the mechanic?
I am sick to my stomach with worry that this is going to cost me more money.
i don't think so, just remember what we talked about or even print it and bring it with you for reference, yea i hear you on the cost, cars suck but we all need them, keep me posted on what happens, thanks jim