keep causing a skip or lugging code P0171

it sounds like the plugs are worn out. pull one and check. good job on the elbow hose, very common failure for those motors.

This guide can help us

https://www.2carpros.com/articles/repair-lean-mixture-codes-p0171-or-p0174-on-some-manufacturers

Roy

The plugs may have around 30k on them had it tuned up June or July of 2010.

did you use platinum plugs??

Roy

I'm not sure they were suppose to have they cost about $8 or 9 bucks a piece. I have been reading about people with the same leak and after the repair vehicle still running rough and they cleaned the MAF sensor and supposedly the vehicles ran great again. I can't believe that after repairing the vacuum leak it still feels like it did with the leak but not as bad. Does the computer take some time to relearn the mixtures after something like this, I've even heard this. Thanks!

YES IT WILL TAKE SOME TIME TO ADJUST THE FUEL TRIM READINGS. I DONT THINK THATS YOUR PROBLEM . SECONDARY IGNITION PROBLEMS ARE BIG. ON A FORD YOU MIGHT HAVE A HARD TIME FINDING A MISS FIRE COUNTER WITH A SCANNER. BUT YOU COULD HAVE SOME ONE SCAN IT IN MODE 6 AND SEE WHICH CYLINDER ARE COUNTING MISS FIRES. THEN SWAP THE COILS TO SEE IF IT MOVES

yes, you can clear the memory by removing the battery cable for about 10 seconds and installing. it may not idle right away till it relearns but it may make it somewhat better.

never a believer about cleaning maf. the carbon is burned into the wire and no cleaner can remove it. if it is out of range, it needs to be replaced.

i still think your issue is secondary ignition.

Roy

I know a coil can go out just like that and some will misfire or breakdown when going out. I guess I can unplug cylinders to see if idle changes any in the morning and go from there. I just ran out and drove it maybe about a mile and the SES light came on. I'm suppose to go to the doctors tomorrow had to cancel appointment today because of truck. I want to thank you for your time and advice and sorry about donating I'm in a heck of a bind here with everything happening all around the same times.

Can a coil cause a P0171 code? I'm not sure if they were replaced I can't remember. The number 3 plug blew out of the cylinder head like so many Fords do back in 2010 when I had them install the new plugs because it had been around 75k then and I know they were the platinum plugs or 100k plugs because I had it tuned up then and I think that was around 100k on the truck.

no, the coil will not cause the 171.

hope we helped you out a little.

Good luck

Roy

I replace the MAF sensor that did it!

let us know how you make out

Roy

It is a 2002 Ford f150 4x4, 4.6L

The Engine Computer alternates from commanding a too rich fuel / air mixture to a too lean mixture a couple of times per second, then it expects to see corresponding changes in what the oxygen sensors detect for unburned oxygen in the exhaust system. In this case there is too much unburned oxygen in the driver's side exhaust and the computer is unable to correct it. Could be a vacuum leak that is affecting one side of the engine more than the other, a partially plugged injector, low fuel pressure, or a misfiring spark plug. Those are some of the common causes. The fault code just gets you to the circuit or system that needs further diagnosis.

I have a po171 code in my car I don't not how to fix
any adias thanks o.p

first check for exhuast leaks on the exhaust piping and manifold before the o2 sensor. if no exhaust leaks

If no exhaust leaks, check for intake leaks on the passenger side of the engine.

I have tried fixing this error for a while, but no luck. According to the print out at Auto Zone, there are four things that may have caused this error, I have done 2, used full system fuel injector cleaner, and cleaned the MAF sensor. The other 2 are o2 sensor problems, and ignition misfire. What do I need to remove the o2 sensors so I can swap them out to see if the error changes? A special tool? or a certain size wrench? Thank you, Justin Garcia Do the sensors look damaged?

I don't see damage, there is a special wrench for this. There is a slot cut into it to allow the wire to not get pinched. The parts sore should have it in stock. The po171 often turns into a MAF sensor, cleaning doesn't always work.

Something else to consider is the fact that you are only recieving lean codes for one half of the engine. Typically MAF failures result in lean codes on both sides of the engine. Since this engine has molded intake gasket you may have a leaking intake. It's not a severe leak since you are not getting misfire codes as would also be the case with inadequate fuel from the injectors. Try spraying a carb cleaner at the base of the lower intake while the vehicle is running. If the engine changes the way it runs then that is your problem. If it doesn't let me know and we can go from there. Either way, you will waste your money if you replace the O2 sensors. I can guarantee that will not resolve the concern. Check the intake on the passenger side and post back the results

The problem started when my brother was driving it. I was in the truck with him, it was nighttime and we hit a puddle going about 65-70mph. About a minute after hitting it, the "service engine soon" light came on. I'll get some carb cleaner and check it out tomorrow. I'll let you all know if I find something out.

- Justin Garcia

i need help with this code i know its a lean issue on bank 1 but what r the steps to eliminate things i already tried replacing the intake( plentum) gasket what else can i do? i dont have much money to keep replacing all these parts . the engine blew going 75 in cruize control so i replaced it with same thing. now it is doing same thing. iam going out to the garage to clean the maf sensor and check the crankcase vent tube ,where is that on this engine? if some 1 can help me solve this problem i will donate whatever u want well almost anything u know what i mean. there is also a long metal tube the diameter of a nickel behind engine going down to the ground well i ft from ground that is not connected to anything and it is not the transmissin dipstick tube but runs along real close to it

Let me know if you need the next step of diagnostic procedures.. Thanks for using 2CarPros.com!

i had to use a pry bar on the egr valve to get it to lalign to the two mounting holes for the bolts to go on and crushed the top of egr valve would that affect its operationand if im right the egr valve is the tube from side of carb so to speak to the exhaust manifold on bank 2 side correct?

how di check for vacume leaks and ca u answer some of the other questions in the paragraph plz ty so much i will try the opts u gave first then i'll ask for more help and plz look 4 me on here to keep me in check and in your mind thx

Sorry about that.. The PCV valve is located under thehood, center upper engine area, top of engine, mounted in passenger side valve cover. To check out your PCV (positive crankcase ventilation) system, perform following procedures..

If any step here leads you to an additional step not posted just let me know and I will get those to you as well.. As for the tube not connected, where is the top end connected? Was this noticed when replacing engine? Perhaps it was forgotten about when replacing the engine or it may just be a drain tube for ventilation tube for some component. Without a picture or more detailed location I am really unsure about it.. To check for vacuum leaks, spray something such as carb ceaner on all vacuum hoses and listen for the RPM's to change. If the RPM changes then you know there is a leak in that spot. Do this to all hoses and visually inspect them for damage/kinks.. Thanks for using 2CarPros.com!

ok now how bout egr thing i asked if it is dented in a bit will that cause it to not operate properly? what does the egr do? can that be the problem? also i did just replace the pcv in valve cover and now it sounds like i have a engine knock really loud. i did nt replace with oem or adequit part just saw one that looked like it and used that. is that normal?

i replaced my old engine with a 2000 mercury grand marquis engine. i had to change the intake(plentum) and the injectors and use my 2 coil packs instead of the coil paks on the spark plug itself. cuz of the intake wouldn't match up to the air intakei had for my truck. is that ok also. what a head ache i have so sick of this. the other engine was doin the same thing then the engine blew 2 cylinders,bent and destroyed 2 spark plugs ruined a coil pak and bent and ruined the lifters well the lash adjusters. i need help so bad. i will try all the things u sugested tomorrow morn and will be looking forward to your answers to my next questions tomorrow morning or mid day sometime.
thx again u r a savior to me if this all works without replacing all the sensors and other related parts until im broke

Pic of EGR valve is below.. it will be ok dented as long as it isn't a huge denting that is smashed it together top and bottom..

No anytime you have an engine knock something is not right. Are you sure you replaced it properly? I always recommend OEM parts but I wouldn't think a different brand part would cause an engine knock.. The intake will be fine. Thanks for using 2CarPros.com!

ok well egr is dented at the top of it where the smallest circle part of it and the pcv valve is knocking when installed stops knocking when i take it out of valve cover and engine bogs maybei should just replace the egr as a precaution and who knows maybe it will be the problem

You can clean the EGR and related components with carb cleaner and brush to get the carbon build up out. This usually fixes any EGR valve related troubles for a temporary amount of time..



Thanks for using 2CarPros.com!

ok i cleaned the maf sensor, i replaced the egr and the pcv valve and replaced all the vacume lines that i saw what else shouldi do? i am going to return the egr vlve as it did not change the way it ran a bit and i could use that on something else that i need . do u think i should replace the bank 1 o2 sensor? or what should i do bext plzzzzzzzzzzzzzzzzzzzzzzzzz help

Ok- My truck kicked the infamous p0171 codes and gave missfire codes on cyl 1 and suffered a major power loss though it has 35" tires with 4.10 gears. I replaced every plug/wire, new coilpack (though it was just a year old) replaced 02 sensors, new MAF sensor, new IAC sensor, new pcv valve, checked hoses for vacuum leaks, new fuel filter, ran seafoam through vacuum line from brake booster to smoke out the system. Still no improvement. I took it to the dealer who diagnosed that everything looked acceptable except cyl 1 failed the leakdown test. Suggested a new motor since the rings were probably shot. I had a new Jasper put in- idled better but still no power on hills/hard acceleration. I decided to go with catalytic converters. Temp tested between the 2 banks and bank 1 (pass side) was extremely hotter. Replaced both sides (all 4 converters) to be safe. Still no power improvement though I had no check engine light. One day later my CEL came on. Hooked it up and it's the same p0171 code saying Sytem Lean on Bank 1. I'm bank at the beginning though my bank account is almost $6,000 lighter. I guess Fuel delivery is my next route...

i went and replaced the pcv valve with the oem and the knocking is fixed but the hesitation, lack of power and rough idle are still there. and i stated b4 in the last reply i replaced the egr and the truck still runs like crap.so im gonna return the egr and put the original one back on and save the 50.00 for the real part. oh and i cleaned the maf sensor and the air filter.

Why did they replace the engine? What was leaking down compression or fuel pressure?

This code simply means additional unmetered air is getting into the engine (By-passing the MAF). Usually, it's caused by a MAF but I see you replaced that. Have you thoroughly checked for vacuum leaks? There is a vacuum hose behind the throttle body that has a 90 degree bend and commonly dryrots.

Also, a faulty DPFE (mounted to the engine) can be the cause. It has two rubber hoses that go to the hose for the EGR. Many times corrosion in the sensor will cause it to under report EGR flow. What happens is the EGR is told to stay open longer causing a lean misfire. Yes, it sould set a PO401 (EGR insufficient air flow), but it is known to many times set the PO171 or PO174.

Let me know what you think. I have to admit, I'm not sure what all the dealer did, but I don't think you needed a new engine. This type of thing really upsets me.

Let me know.

Joe

also i thought i would mention that when i unplugged the maf sensor the engine did die therefore it is working properly

Well the dealer didn't replace the motor. They only noted that cylinder 1 was showing much lower compression, like 60 lbs I believe. They also said that it was leaking down which was probably a sign that the rings were shot (Im assuming compression) and they suggested a new long block. This was after I had replaced all of the sensors and what not, so I figured this could possibly be where the misfire was coming from. If it had no compression to respond to the combustion, then the computer would read it as a misfire, this causing the lean condition on that bank. We decided cyl 1 was so shot that a new motor was needed anyways, and could be a cause for the power loss. So I took it elsewhere for the Jasper swap. Myself and a couple of family mechanics checked for vacuum leaks prior to the dealer visit. I had already changed the pcv valve and inspected the hoses/elbows coming from the pcv to the throttle body and around the EGR. Wouldn't the DPFE kick a lean code for both banks? Should I buy an injector and try it on cyl 1 since that is where all of my problems have shown? What about vacuum leaks on the brake booster? Wouldn't that cause both banks to read lean though?

[quote:2b291135b5="miamiii13"]also i thought i would mention that when i unplugged the maf sensor the engine did die therefore it is working properly[/quote:2b291135b5]i also need the next step after the #41 u gave me.

From what I have delt with, the DPFE will cause a lean mixture on both banks. What it does is corrode inside. As a result, it doesn't sense properly and causes the EGR to stay open longer than it should. Thus, you get a lean mixture. As far as a vacuum leak at the brake booster, yes, it will cause a lean mixture on both banks.

I'm glad the dealer didn't take you. I would have done a wet compression test if it was a valve or the rings. Rings would have cost you a hundred bucks if you did it. As far as a valve, remove the head and reseat the valves. I just hate when dealers tell customers they need a new engine when it can be a cheap, easy fix. Sorry if I sounded upset.

Let me know if you have other questions. My guess is the DPFE is setting the code. Keep in mind, if you had a cylender that wasn't firing, the O2 sensors should have thought it was running rich because there would have been unburned fuel.

I'm here if you need anything. Let me know and I'll do my best to help.

Joe

A lot of steps here okay so read carefully and if it leads you somewhere different let me know so I can post it further.. I know it seems like a lot of time consuming trouble but it will save you a lot of money in the end..

Thanks for using 2CarPros.com!

Thanks so much for the quick replies. I probably should have looked more into the possibility of it being a valve. Esp since the catalytic converters on bank one clogged. However, I didn't have the time to put into pulling the head since I just moved and don't have a garage here and needed my truck back asap for work. I know that cylinder 1 was firing electronically, but I'm almost convinced there was an absence of fuel there causing the lean reading. I'm going to buy one injector tomorrow, disconnect the battery to reset the computer, pull the fuel rail and replace the injector on cylinder one. Hopefully that is going to be the root cause of everything. **Injector clogs/leaks, causes misfire, caused catalytic converters to clog after driving for way too many miles running lean while trying to troubleshoot, then the exhaust backed up, burnt the valve and caused the cylinder compression failure.** This is my theory anyways and I may be completely off. But I have way too many custom hours/money into the truck to turn back now. Yea I could have bought another truck for what I have into it, but atleast I will know what has been done to this truck! Any ideas if the new injector doesn't fix the problem?