What could cause a car to fail a smog test?

Question

how much money would it cost at the most to repair a car so that it can pass a smog test?

Answer 1

Yeah, your question has ALOT of answers, if you could explain more in depth that would be great!

Answer 2

depends on the type of failure. the cheap side of it, timing is off, get that adjusted and you are good to go. on the higher side of it, an engine worn to point of very low compression, it will need to be replaced or rebuilt.

Answer 3

Depends on what all is wrong with your car.

Answer 4

Depending on what year it is, I would say catalytic converter could be clogged or a number of other things. Or it could be that you have a smog pump that isn't working properlyy. No telling what it would cost without telling what kind of car you have. I would just go throw and replace everything, it shouldn't cost that much and it will be betterr for your fule ecomomey in the long run also.  

Answer 5

what did it fail on?

there are just too many answers...

o2 sensors, cat-converters, tune-up components, sensors, blowin' blue.....

you need to go through the test, if you fail, that will give the repairman an idea of what needs to be repaired.