Q: I keep getting OBD-II codes P0171 and P0174

asked by on

I keep getting the P0171 and P0174 lean bank 1 and 2 code. When I fogged the intake the only smoke came from the press cap on the idle air control valve, I did this on my 02 F-150 with a 5.4 no smoke. When I say press cap I mean the cap on he valve that looks like a freeze plug crimped over the valve. Is this normal, since taping around the valve I haven't had the check engine light for over 300 miles.

My car has 203500 miles.
My car has an automatic transmission.

Since you have codes that both banks are lean then the problem will most likely be from air entering the intake manifold after the mass air sensor. The idle air control valve should not have any air leaks from the valve and may be contributing to the codes you are getting. It would be recommended to scan the computer data to see if the mass air sensor is registering the correct barometric pressure reading. This reading should show the proper pressure for the altitude your vehicle is at. If the data is reading that you are above more than 1000 feet more than what you are at then the mass air sensor is causing the codes and the mass air sensor needs replaced. The mass air sensor can be damaged by an air filter that is the oil bath type and should be the dry type filter. Replace the air filter if it is incorrect type or is dirty restricting air flow into the engine.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. I keep getting OBD-II codes P0171 and P0174

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: My car wouldn't start after battery was just replaced my car cd player is running after I turn the car off

Your CD player definitely should not be running after the key is off and out of the car. It will certainly drain your battery. So the good news is you can be reasonably certain about what is killing your battery....

Q: Low oil pressure code rough idle

You will need to have the low oil pressure code diagnosed. The engine will go into fail safe mode when these problems happen in order to protect the engine. Depending on the specific problem found, the engine may idle low...

Q: Engine is running rough and P0401, P0171 and P0174 codes.

The first thing to check is to see if the EGR solenoid will release the vacuum when the electrical connector is disconnected. If it still doesn't release the vacuum then the solenoid should be replaced. The codes need to be...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
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...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...