Skip the auto shop - Our mechanics make house calls

Q: Check Engine Light with P0174 code

asked by on

Check engine light came on last week. Car was running ok, but it needed to be checked. Had code pulled and it was P0174. I changed the PCV and cleaned the MAF with MAF cleaner. The next day after, the car had rough idle start and very sluggish acceleration. The symptoms do improve after the car warms up. Mpg is noticeably worse

My car has 198000 miles.
My car has a manual transmission.

A: As you know, this code relates to a lean fu...

As you know, this code relates to a lean fuel condition which can be caused by many different things, some of which you have already addressed. 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 reading, this information is relayed to the car's ECU which then makes a determination as to whether or not to add more or less fuel to the engine. When too much or too little oxygen is present, this will cause check engine light to come on.

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.

Too 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.

When the O2 sensor is not working properly, this will cause false readings to be relayed to the computer causing inaccurate adjustments to be made to the intake and fuel system in your engine. I would suggest having an expert from YourMechanic come to your home to diagnose the cause of the Check Engine Light in person so this gets repaired correctly.

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・Save up to 30%

Get a quote

What others are asking

Q: transmission (ax4n) is not going into overdrive

You will need to have the transmission tested to see if the transmission solenoid for the torque converter lock up solenoid is stuck or bad. The transmission fluid should also be checked to see if it is full of clutch...

Q: I' trying to start my vehicle and it made a loud clacking noise and the battery is drained

Hello. If the vehicle produced a clicking clacking sound when the key was turned then it may be possible that the battery or starter are the issue. A faulty, or low battery will cause the starter to click if it...

Q: Issue with throttle position sensor and Check Engine light is on.

I'm not quite sure what to make of this description, but I'm guessing you are trying to say the check engine light goes off and on intermittently with a code stored for the throttle position sensor (TPS). I do not...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
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...
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...