P0171, P0174 Codes
 

I'm relatively new to this site and would greatly appreciate any information you can give. I admit, I'm a novice when it comes to auto repair. However, I'm an eager do it yourselfer not afraid to get his hands dirty.

Anyway, yesterday when I started my truck (2003 4.6L V8) it began to run rough at idle then almost died. I gave the gas pedal a pump, which helped for a moment, then the rough idle started again, followed by a surging of the engine. The service engine light came on. I took it down to the shop and was given the following codes

P0171...System too lean bank 1
P0174...System too lean bank 2

I was told that because bank 1 and 2 codes set together, that it was likely a faulty MAF sensor.

Again, any and all input would be greatly appreciated.

Thanks for your help.
Smjacobe

Those two codes together usually mean the MAF is dirty/ faulty or there is a significant vacuum leak which could be from a leaky intake or a broken vacuum line. There are other causes but those are the most common. I'd start by cleaning the MAF.

Thanks kozal01...I will start there and see how it goes.

Cleaned the MAF and no luck...still running rough. I did notice that in the morning when its cold, the engine runs better, after a few minutes when it warms up is when the rough idle starts. Not sure if that is helpful in anyway, just thought I would mention it. How do I go about checking for a leaky intake? Someone also mentioned a failed oxygen sensor...any possibility with that being the culprit? Also, I did fill up my gas tank just prior to this starting...how about a simple case of bad gas?

I believe you can use a can of intake cleaner, or something like that, and spray around the engine area and listen to the engine idle speed. The engine speed will change if you spray near the leaking hose/fitting area. Don't use ether, since you cause more problems than you already have. Also, don't spray half a can in one spot! You need to move the spray pattern area around to locate the leak. Good luck.

Glad I found this one I'm having the same issue. I've done a few upgrades. Wondering if that has anything to do with it. I was told the same thing that could cause it.