P0171 Error

[mikeexpedition]

I have had a check engine light on for months now (p0171 error code according to AutoZone). I took it into a shop and they replaced the MAF ($350 I'm new to this so I didn't know you could try and clean it). Anyway it came back on a couple days later. So I am lazy and wait a few weeks and take it back. They then tell me that "cold air could cause it to come on." So they reset it. It comes back on a couple days later again and this time I wait a few months to take it back.

Now its apparently the manifold gasket that needs to be replaced. Of course it's going to be almost $500 (only $6 and change for the part). I know it's a big project to get to, but anyways, now I'm thinking they are cheating me and I start looking up reviews online and see that apparently a lot of people are not happy at all with this place. Someone said they were told they needed new rotors and brakes without knowing this person had them replaced a week prior.

Back to the problem... My mileage is normal for what the estimated mileage should be. There's no rough idling. Nothing obviously wrong with the way it runs or handles besides the check engine light being on. Any ideas on what it might be? I hear the gasket is common with this vehicle but I'm hoping they are wrong and it's something else.

2001 Expedition 5.4 engine Eddie Bauer Edition
Recent Changes (all after the check engine light came on):
Fuel Filter (fuel came out black from the filter after changing)
Air Filter
MAF

 

[Maverick1701]

possibly a vacuum leak somewhere after the MAF sensor? Might even be a bad o2 sensor

 

[mikeexpedition]

Thanks for such a quick response.

I'm new at this whole car fixing thing so... is there any easy way to see if it is a vacuum leak or a way to see if the o2 sensor has failed? Most of the other threads are showing this code in combination with another code so I don't mislead anyone. This is the only code I am getting.

 

[FordandPolaris]

If you have a vacuum leak, the engine will probably be running rough at idle. Things such as pop cans etc. with be shaking in the cab. As far as the O2 sensor goes, there is no real way to tell which one is causing the problem. There are probably 4 in your truck (there are 4 in my 97). If you are feeling adventurous, look up some how-to vids on youtube about replacing a car's O2's. It isn't a hard job, and it is worth trying yourself.

If you do have the rough idle mentioned before, here is a link to a thread that helped me fix the same problem.

http://www.expeditionforum.com/f27/rough-idle-p0171-p0174-heres-what-you-need-check-first-4926/

 

[Maverick1701]

another pretty easy way to look for a vac leak is to grab a can or two of carb cleaner and start spraying it around your vac lines. If your idle changes then you are in the area of the leak.

 

[Big Red Monster]

check your differential pressure feed back sensor, this thing is on the left side of the throttle body and there are 2 rubber hoses that come out of it, mine were both rotted out and it was giving me that damn code saying "bank 2 running lean" the mechanic wanted to change my intake manifold gasket which woulda been over 800, i spent 5 bucks and fixed the problem.

 

[splintrcel]

I wouldnt go around spraying carb cleaner in the engine because that wrecks rubber so bad. A little bit wont hurt but i work with carb cleaner and brake cleaner for washing production parts at work (CNC Machine Shop) and it eats rubber and destroys it.

 

[tsgrpr97]

Check your accessory vacuum lines into the cab and down to the vac resevoir these can rot and leak.

Sent from my LGL55C using Tapatalk 2

 

[Exia]

P0171: System Too Lean Bank 1.

PCM's Adaptive Fuel Strategy has reached its Rich calibrated limit for Bank 1.

In plain English, this means that the PCM has detected a Vacuum Leak (it may be real or perceived) and is compensating by injecting the maximum amount allowed (under its program) of Fuel into the Cylind ers for Bank 1.

The very first thing you need to know, about these two Diagnostic Trouble Codes (DTC), is that they do not accuse anything specific as being BAD. In other words, they are only describing a condition in which the Computer is seeing an unmetered amount of air entering the engine, that no matter how much Fuel it dumps (into the engine), it can not compensate for it.

This unmetered air entering the Engine is usually due to a very large Vacuum leak... but not always and this is what complicates things a bit. Several things can fool the PCM into thinking there is a Vacuum Leak, like a failing Oxygen Sensor or even a very dirty MAF Sensor.

And so, the bottom line is that several different things and conditions can cause these Diagnostic Trouble Codes to pop up and light up the Check Engine Light (CEL) on your Ford pick up or SUV.

Part 2 -P0171, P0174 Testing Tips (Ford 4.6L, 5.4L). System Too Lean Tests.

 

[mikeexpedition]

Thanks for all the input everyone... I've never signed up for a forum for anything before. I'm very impressed with the quick feedback and knowledge with this one though. I'll keep working on it and let everyone know the end result.

 

[Captain Morgan]

Thanks for all the input everyone... I've never signed up for a forum for anything before. I'm very impressed with the quick feedback and knowledge with this one though.

Thank you we accept VISA, AMERICAN EXPRESS, MASTERCARD and PAYPAL.



Fine bunch here for sure.

 

[Exia]

Thank you we accept VISA, AMERICAN EXPRESS, MASTERCARD and PAYPAL.



Fine bunch here for sure.

Don't forget cookies and a glass of orange juice

 

[Big Red Monster]

Thanks for all the input everyone... I've never signed up for a forum for anything before. I'm very impressed with the quick feedback and knowledge with this one though. I'll keep working on it and let everyone know the end result.

reason you got such quick feedback on this problem is because damn near all of us have experienced this problem already lmao

 

[mikeexpedition]

UPDATE.......

After speaking with a friend, he said that because my old fuel filter dumped out black dirty gas when I changed it, I may not have been getting fuel all the way through bank 2 to bank 1. Thus creating a bad gas/air mixture and running lean. Also he thought my fuel injectors may be a bit clogged because of the dirty fuel filter so I've run some cleaner through it and he reset my CEL. I've done about 75-80 miles since and no CEL light. Hopefully it stays off and I save myself from doing a $500 manifold gasket change.

SIDE NOTE: I did my front air shocks today (first time ever doing shocks and did them by myself). Woohoo.... The first one took about 5 hours then I realized that I don't have to be all that gentle and sometimes a sledge hammer is appropriate. Especially when the bolt seems to have fused the threads to the rest of the metal. I literally tried cutting it out (apparently sawzalls can't fix everything). Second one took less than 30 minutes.

Thanks again, I'll update further if it isn't fixed and let you know what the outcome was for my P0171 code. Hopefully soon I'll be able contribute back as much info that has been contributed to me.

 

[Exia]

Best way to help your fuel fill it up and pour some lucas fuel stabilizer in it

 

[jdan]

Search my threads. This may help.
I'd give you a link but it's kinda hard to on a phone.
This thread explains how common PCV hoses rot and cause symptoms like yours.

 

[mikeexpedition]

I think my buddy told me to use sea foam. I've been using Lucas here and there especially after the CEL came on but it was before the filter change. What cleaner do you guys prefer?

 

[Exia]

I think my buddy told me to use sea foam. I've been using Lucas here and there especially after the CEL came on but it was before the filter change. What cleaner do you guys prefer?

Lucas, in my opinion is the best, unless you want to buy about 5 bucks of 100+ Octane to put in it. Only do that once a year and only add about 1/3 to full tank. And yes 100+ Octane is race fuel

 

[tsgrpr97]

The effectiveness of bottle additives is hotly debated. If you're serious about cleaning the top end and injectors take it to a service station with a motor vac machine. During the service they first physically clean the throttle body and intake, then they pull the feed line from the pump and attatch it to the machine and the machine to the vehicle. The vehcile runs while the machine fills up with gas from your tank. While this is going on the mechanic also measures fuel pressure. When the machine is full, the feed and return lines from the vehicle are put on a closed loop so the pump can run un interrupted throughout the service. Meanwhile the machine has mixed the gas with detergents etc. (Motorvacs formula). The feed and return lines from your fuel rail are connected to the machine and the motor is started and runs on the concotion for a half hour or so. The additives don't burn during combustion they vaporize. Costs between 100 and 200. Pouring sea foam in through the pcv hose is sort of the same principal, but the motor vac is a more thorough and effective approach.

Also, imho depending on the design of your intake liquid seafoam will just pool in the intake instead of vaporizing into the chambers. Lots of smoke from it burning off but not real great results. They also make a spray cleaner to spray into the intake and that WILL get into the combustion chambers and work. But the motor vac is still more thorough than this. I've read TSBs recommending the spray cleaner approach for carbon buildup in the top end.

Sent from my LGL55C using Tapatalk 2

 

[Exia]

Costs between 100 and 200.


Sent from my LGL55C using Tapatalk 2

Yes it takes 30 minutes, but you didnt factor in the 2 hours labour fee that dealerships will charge thats an extra ( dependin where you live ) 79 to 89 bucks an hour.

I have been through that with my brothers SRT8 Challenger, they charged 400+ for the fuel system flush. But again different places different prices.

To be honest the additive you use is your choice, one person will say, STP, and another seafoam, or suggest evasive $200 to $300 procedures, try different things, once you find what your looking for and it works for you use it. In the long run we can suggest things, but each person has their own preference.