Skip the auto shop - Our mechanics make house calls

Q: O2 sensor or converter, ECM, or harness?

asked by on

Two O2 sensors are bad in the codes also saying low flow. The engine has a very rough idle once started to the point of stalling. Once it's moving it really runs quite well with almost no noticeable problem. Only at idol us it noticeable and very noticeable it is.

My car has 159000 miles.
My car has an automatic transmission.

As you may know the oxygen sensors which are part of your emissions system read exhaust gases to determine whether or not the appropriate amount of oxygen is present in the exhaust. Based upon this information, the ECU then makes fuel adjustments to the engine. Too much oxygen may be present in the exhaust gas due to things like an exhaust leak, a vacuum leak, a faulty mass air flow sensor (causing a lean fuel condition) or faulty fuel injectors. To little oxygen may be present in the exhaust gas may be caused by things like a clogged air filter, a failing mass air flow sensor (causing too much fuel to be introduced to the motor), bad fuel injectors or a clogged catalytic converter. I would suggest having an expert from YourMechanic come to your home to diagnose your emissions system.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 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

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: Coolant goes down, no leaks 2004 Nissan

Hi there - if the coolant level is dropping, it's either leaking somewhere that is undiscovered thus far, possibly evaporating before it is discovered, or the engine is consuming it via a blown head gasket or crack in the head...

Q: My car won't start. All the lights work, there is just a single loud click when I try to start it. Is it the starter?

If the starter is accessible under the hood, grab a friend and a small hammer. While one of you tries to crank the engine, have the other lightly tap the starter at the same time. It is possible the starter...

Q: are upstream and downstream O2 sensors the same

Hello there, the upstream and downstream oxygen sensors for your 2013 Chevrolet Cruze are not the same. The upstream oxygen sensor is located before the catalytic converter and is used to help calculate the air fuel mixture, and is often...

Related articles

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...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...