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Q: Failed the emission test. I'm suspecting a bad oxygen sensor.

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Took truck through emissions failed by 800 points on both Idol and and rolling dynoRPM test truck seems to run ok has lots of mileage on 02 sensor engine doesn't have any misses has high mileage but seems to run OK doesn't burn any oil I'm thinking that it 02 sensor might be bad it only has one in front of the cat cat is new OBD2 . , has throttle body fuel injection which seems to be working fine we just replace the air filter and I'm waiting on the oxygen sensor to run it through again. Plugs are new I'm going to change the plug wires and the rotor and cap also before I run it through If it fails again I guess I'll go for the waiver because in Arizona after you spend $300 on a vehicle from 88 to 95 you can get a waiver only good for one year. Sucks because I like the truck but yet I might have to dump it for nothing if I can't get it through emissions and I don't want to do that I'm not a rich man thanks for your help any help is appreciated even if you can't thanks mike

My car has 210000 miles.
My car has an automatic transmission.

A: Hi there. Change out the spark plug wires, ...

Hi there. Change out the spark plug wires, put sea foam in the vacuum system to clean the internals of the engine and change the oil and filter. Then drive the vehicle around and fuel up with Techron fuel.

When you go to the emissions station, run the engine hard, but not enough to damage it. This gets the catalytic converter hot and makes it work real good. When in line, do not shut off the engine and keep it running. Try to be the first in line if possible or early in the morning when the line is short. This will help with after driving around hard. Your truck should pass emissions with a good outcome.

If you need further assistance diagnosing your engine, then seek out a professional, such as one from YourMechanic, to inspect your exhaust system and help you with preparing for the emissions test.

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