Q: RPMs erratic during idling, Check Engine Light on, P0174 code

asked by on August 31, 2016

The RPMs are fluctuating erratically while the truck idles. It is similar to the AC compressor turning on and off. The dash is showing the check engine light on too. The truck has been getting very low gas mileage, like 13-16 MPG. After having the codes read, the P0174 error code appeared. The repairs done on the truck so far include the replacement of the oxygen sensors, gas cap and MAF. Also, the cleaner was added into the fuel injection system. What is causing this and what does the error code indicate? What kind of repairs are necessary on the truck?

Hello. The P0174 code deals with the truck running lean. That means that the PCM is restricting fuel to the injectors. This is usually caused by a vacuum leak in the engine. There could be a leaking intake gasket, or a broken or disconnected vacuum hose. The may cause the truck to run lean and have an erratic idle. I would recommend that you have the intake and vacuum lines to the car checked for leaks and breaks. Have a certified technician, like one from YourMechanic, diagnose the idling issue and assist you with repair.

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

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

Unable to go past 70-80 Km when going up a hill. Code P0174 with flashing engine light

Hello. A flashing Check Engine Light is an indicator that the computer has detected an issue that may potentially cause harm to the vehicle's emission system components. The code P0174 indicates a lean condition on bank 2 of the engine....

On my 2000 ford explorer do i need to replace the ball joints and the control arms or can i just replace the ball joints

The lower ball joints on this vehicle can be replaced individually. The upper ball joint is usually included with the control arm but, depending on your VIN, the upper joint is available separately as well. You should examine the bushings...

Car shaking when it goes above 45-60mph and stays in that condition with check engine light flashes

Hello, and thank you for writing in. The vehicle may be having one of many issues. Shaking is usually caused by some kind of imbalance with the engine and its combustion cycles. This may be a problem with the fuel...

Related articles

How Do Sensors Get Dirty or Damaged?
Car sensors measure and relay vital information to the ECU. Some sensors can get dirty from normal use, or fail if the car overheats or has a problem.
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the P0052 code means This code is seen when...
Where Is the O2 Sensor Located?
Oxygen Oxygen sensors O2 sensors will always be located in the exhaust system. Their function is to sense how much oxygen remains in the exhaust that is flowing out of the engine, and report that information to the vehicle’s engine...