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?

Car idle is rough Inspection $94.99 - $114.99 Get a Quote

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.

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


Experienced Mechanic?

Earn up to $70/hr

What others are asking

How do I check and refill the window washer fluid?
Window washer fluid helps keep your windshield clean and clear of debris. It ensures that your wipers are able to remove grime, dirt, dust, and even oil and other fluids that get onto the windshield from the road. Of course,...
How do I use an iPod with the infotainment system?
You can play an iPod through the infotainment system by connecting it via an AUX cable or a USB cable. Both the AUX and the USB cables connect to the ports in the center console. While an AUX cable will...
if my alternator fuse is blown would it make sense for my car not to start?
Unfortunately, the mistake of hooking up the battery cables in reverse may have causes several sensors, relays, and electrical components to be damaged during the attempted jump start. There are most likely multiple electrical issues that need to be diagnosed...
Im not sure if its the tie rods that are bad or if its the cv axle... it doesnt click or anything
Typically, if you feel "slack" in the steering, the rack and pinion (https://www.yourmechanic.com/services/steering-rack-gearbox-replacement) (or other "steering gear") unit is worn but the tie rod ends (https://www.yourmechanic.com/services/tie-rod-end-replacement) (inner and/or outer) could be implicated as well. Vibration or shuddering on application of...
Three of my Civic's power windows fail to operate simultaneously. are they having the same power switch problem?
Hello, thank you for writing in. At first it sounds as if the "child locks" have been turned on, make sure this is not the case. The power for the windows comes from the main and under dash fuse boxes,...
Reduced engine power 2004 Chevrolet Tahoe 5.7L
Hello - the reduced power mode (https://www.yourmechanic.com/article/is-it-safe-to-drive-with-the-reduced-power-light-on) your truck drops into is electrical in nature, and most often a problem with bad ground wire connections between the engine and chassis, and the chassis and battery. This is a wide-spread issue...
I just had a diagnostic performed on my car and the following error code came up P0299 boost control sensor.
Hi there. Check to see what the oil pressure is in the engine. If the oil pressure is low, then the P0299 (https://www.yourmechanic.com/article/p0299-obd-ii-trouble-code-turbo-supercharger-underboost-condition-by-spencer-clayton) code can appear. Also, check for the EGR operation and see if its sticking. A faulty EGR...
Used a quick fix for my broken power window: hold switch up and slam door. What might need replacing if it worked for me?
Hi there. In most cases, the quick fix that you learned online will lead you to knowing what component was damaged. In this case, if you press a window switch and slam the door, it will shake or rattle the...
I changed my spark plugs due to p0300 for 2013 infiti
Hello, thank you for writing in. The vehicle originally gave you a code for a misfire. It could have been caused by the spark plugs or a fuel problem. The second code pertains to a low fuel pressure being detected....

Related articles

P0063 OBD-II Trouble Code: HO2S Heater Control Circuit Low (Bank 2 Sensor 3)
P0063 P0063 trouble code definition Trouble code P0062 indicates that the heater element used to heat up an oxygen sensor has malfunctioned. To switch on an oxygen sensor either a power or a ground is supplied to the sensor. A...
P0041 OBD-II Trouble Code: O2 Sensor Signals Swapped Bank 1 Sensor 2/ Bank 2 Sensor 2
P0041 P0041 code definition P0041 tells us the ECU has detected swapped sensor signals for oxygen sensor 2 between banks 1 and 2. This code may be associated with P0040. What the P0041 code means P0041 means that the engine...
P2219 OBD-II Trouble Code: NOx Sensor Heater Control Circuit Low Bank 2
P2219 code means there is an abnormal reading within the NOx sensor circuit voltage often due too faulty fuel usage or defective sensors.