FAQ: P0171 Lean Condition

I have done all my own work im just at the point where im fighting to keep gas in the car its getting sickening when im putting in 65 dollars before next payday ... I took it to the guy to see if he had a fuel pressure tester and he came up with that idea... im not much of a mechanical kind of person but I do what I have too...but I did just check the egr and the issue lies between there im guessing I spike at egr and at the manifold where the egr hose goes too so im stuck

I just sprayed the bottom of the egr, and the car damn near wanted to cut off. so the egr is sucking in plenty of air. thus this shows me shows me I still have leaks in the system thanks guys

well my egr pipe should be here soon, im using that gasket idea for sure when it arrives ,i also picked up a maf sensor for a good price if this doesnt clear the code then im stumped

h20man wrote:

well my egr pipe should be here soon, im using that gasket idea for sure when it arrives ,i also picked up a maf sensor for a good price if this doesnt clear the code then im stumped

what site did you order the egr pipe from

I found one on ebay

Alright guys I'm really stumped, I changed my egr pipe and mass air flow sensor and the p0171 set, I even changed my intake back to the stock airbox and it set... So any ideas would be very much appreciated or if anyone knows how to fool the obd emissions test before I pay a shop to diagnose the problem ....

I assume you cleared the code after changing the erg and mass sensor?

Spray for vacuum leaks?

96_Juggernaut wrote:

I assume you cleared the code after changing the erg and mass sensor?

yup cleared them before starting it and deekster yes I sprayed starting fluid on the vacumn lines and found a leak in the egr pipe, replaced that still getting a code

i havent updated this in a while but yes i still have the code. i went through and replaced my intake gaskets and blower gaskets again and it still set the light. Whats funny is the code only sets at a stop or when im braking, today going back to work after lunch my brakes let go, the pedal went to the floor but i was still able to stop thankfully. long story short we decided i need a master cylinder, maybe im going nuts but im making some sort of connection to failing brakes which obviously operate on vacuum and my p0171 code

the brakes will still function without vacuum, the vacuum just "assists" with making the pedal easier to push.

But do you think a leak coming from the brake system is triggering a lean code?

h20man wrote:

But do you think a leak coming from the brake system is triggering a lean code?

now that on the other hand could, I would imagine if the brake booster itself had a leak it could pull in the extra air.

The brake booster is vacuum actuated. If the booster diaphragm had a leak that would be your vacuum leak. Try disconnecting the brake booster and capping the opening, see if your code goes away. (your brakes will be non-power assist, watch out! Actually I can't recommend this, but it would answer the question)

Instead, try spraying a little carb/brake cleaner around the booster and see if it affects the way your engine runs.

Ill have to try that thanks guys, I did plug the booster hose in hopes of driving it around trying to see if the code will set but my master cylinder is bad so I really didn't have any brakes at all :/

Without the booster, the brake pedal will be hard as a rock, and you will have very little braking. That is normal

I replaced my master cylinder so I just need to bleed all four brakes and the car will be back on the road, I'm talking to a guy from sinister performance who is kindly helping me diagnose this problem, he said check for exhaust leaks and he thinks I got the wrong maf sensor. Any way to check for exhaust leaks besides listening?

Ummm...the only kind of exhaust leak that can possibly cause a P0171 code is if the leak is before the control O2 sensor (manifold, crossover pipe). You would most definitely hear a leak like that if it were big enough to actually cause a code to be tossed....

oh ok, than exhaust is ruled out ive never heard any leaks in my system, i asked to send my pcm to sinister so he can remove this code permenantly and do a standard tune, could that force my car to run lean even if he adds more fuel my tune? car seems to run great as is until the code sets, then the idle gets choppy

That, is a terrible idea. P0171 is there to protect the car. The circumstances for a lean condition can potentially grenade your engine. If it runs lean enough, say bye bye to the tops of the pistons. Lean, along with heat, is exactly what creates spark knock. You seriously need to figure out why it's running lean before you go modding anything.

There is obviously a problem, somewhere. Just because it isn't obvious doesn't mean it doesn't exist. P0171 code can be a bitch to diagnose sometimes. It's like trying to hunt down a ghost. But, you need to find this ghost and get rid of it for your engines sake.

Ahhh the infamous p0171 tricky bs little thing makes headaches worth while...

I've literally spent about a grand diagnosing this problem, I really have no clue what It can be anymore

Well, it appears you're at your limits. If I were you, I would take the vehicle in to a trusted shop, maybe even the dealer, and tell them what's going on, and what you've done/replaced. At this point, I really don't think you have any other options. It needs to be right before you start modding.

Aww nah a grand thats almost impossible ... not unless you bought a new motor damn. Its time for some automotive maintenance help dude

Abaddon wrote:

That, is a terrible idea. P0171 is there to protect the car. The circumstances for a lean condition can potentially grenade your engine. If it runs lean enough, say bye bye to the tops of the pistons. Lean, along with heat, is exactly what creates spark knock. You seriously need to figure out why it's running lean before you go modding anything.

This is the most important paragraph in this entire discussion. DO NOT disable the P0171. Find it and fix it.