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

asked by on

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.

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.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1,000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!
  1. Home
  2. Questions
  3. Failed the emission test. I'm suspecting a bad oxygen sensor.

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: How do I fix the issues related to code P0445 (Failed Emissions Test)?

Diagnostic Trouble Code P0455 has causes in addition to a faulty or loose gas cap. In your circumstance, the first thing you should do is reset the Check Engine Light which will erase the existing codes. Then see if the...

Q: Rough running engine also choppy

You may need to have additional diagnosis done by a mechanic like one from YourMechanic to see if the ignition timing is correct and there is no engine vacuum leaks in the intake or vacuum lines. Also to verify all...

Q: No power and stuttering

Hi There, It sounds like you may have a fuel pressure problem related to a faulty fuel pump or fuel pressure regulator. As you know, when you turn the key to on, the fuel pump is activated and the fuel...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...