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Keep causing a skip or lugging code P0171

Tiny
BUCKBASS
  • MEMBER
  • 2003 FORD F-150
  • 177,000 MILES
Had a code P0171 only and repaired vacuum leak. What could keep causing a skip or lugging type feeling driving the vehicle after repairs to leak and can I fix it?

I have a 2003 Ford F-150 and just recently it started running rough like it wanted to stall out at stops and had a skipping type feeling while accelerating. I had a parts store check the check engine soon light and a P0171 code appeared. I found a vacuum leak at rear of intake at the elbow on the pvc valve hose. I replaced the hose and cleared the computer and it still has the lugging or skipping feeling while accelerating.

I would appreciate some help if you don't mind on what you guys think it can be. I don't know if cleaning the maf sensor will help or not, truck was running great until the vacuum leak started and I really do not have the money because I have been out of work for over a month because I was diagnosis with terminal cancer and had my left kidney removed and cancer is in my right one as well but just has started attacking it and there is no cure for my type of cancer.

Sorry to bother you guys with my personal problems but any help would be very much appreciated because I'll be doing this myself. Thanks!
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Wednesday, May 2nd, 2012 AT 12:16 AM

81 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
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
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Wednesday, May 2nd, 2012 AT 12:21 AM
Tiny
BUCKBASS
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  • 6 POSTS
The plugs may have around 30k on them had it tuned up June or July of 2010.
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Wednesday, May 2nd, 2012 AT 12:41 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Did you use platinum plugs?

Roy
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Wednesday, May 2nd, 2012 AT 12:44 AM
Tiny
BUCKBASS
  • MEMBER
  • 6 POSTS
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!
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Wednesday, May 2nd, 2012 AT 1:22 AM
Tiny
DJCL
  • MECHANIC
  • 767 POSTS
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
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Wednesday, May 2nd, 2012 AT 1:31 AM
Tiny
ASEMASTER6371
  • MECHANIC
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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
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Wednesday, May 2nd, 2012 AT 1:32 AM
Tiny
BUCKBASS
  • MEMBER
  • 6 POSTS
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.
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Wednesday, May 2nd, 2012 AT 1:46 AM
Tiny
BUCKBASS
  • MEMBER
  • 6 POSTS
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.
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Wednesday, May 2nd, 2012 AT 1:51 AM
Tiny
ASEMASTER6371
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No, the coil will not cause the 171.

Hope we helped you out a little.

Good luck

Roy
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Wednesday, May 2nd, 2012 AT 2:00 AM
Tiny
BUCKBASS
  • MEMBER
  • 6 POSTS
I replace the MAF sensor that did it!
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Wednesday, May 2nd, 2012 AT 2:02 AM
Tiny
ASEMASTER6371
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Let us know how you make out

Roy
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Wednesday, May 2nd, 2012 AT 2:09 AM
Tiny
FFFSSS
  • MEMBER
  • 11 POSTS
  • 2002 FORD F-150
  • 233,000 MILES
It is a 2002 Ford f150 4x4, 4.6L
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Sunday, December 13th, 2020 AT 1:18 PM (Merged)
Tiny
CARADIODOC
  • MECHANIC
  • 33,916 POSTS
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.
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+1
Sunday, December 13th, 2020 AT 1:18 PM (Merged)
Tiny
OMARYESICA
  • MEMBER
  • 1 POST
  • 2002 FORD F-150
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 11,083 MILES
I have a po171 code in my car I don't not how to fix
any adias thanks o.P
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Sunday, December 13th, 2020 AT 1:18 PM (Merged)
Tiny
BLACKOP555
  • MECHANIC
  • 10,371 POSTS
First check for exhuast leaks on the exhaust piping and manifold before the o2 sensor. If no exhaust leaks
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Sunday, December 13th, 2020 AT 1:18 PM (Merged)
Tiny
FLEXY5
  • MECHANIC
  • 512 POSTS
If no exhaust leaks, check for intake leaks on the passenger side of the engine.
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Sunday, December 13th, 2020 AT 1:18 PM (Merged)
Tiny
PLATINUMKANIKAS
  • MEMBER
  • 2 POSTS
  • 1999 FORD F-150
  • 6 CYL
  • 2WD
  • MANUAL
  • 102,500 MILES
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?


http://www.2carpros.com/forum/automotive_pictures/164623_o2_sensor_1_1.gif



http://www.2carpros.com/forum/automotive_pictures/164623_o2_sensor_2_1.gif

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Sunday, December 13th, 2020 AT 1:18 PM (Merged)
Tiny
SERVICE WRITER
  • MECHANIC
  • 9,123 POSTS
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.
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Sunday, December 13th, 2020 AT 1:18 PM (Merged)
Tiny
FLEXY5
  • MECHANIC
  • 512 POSTS
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
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Sunday, December 13th, 2020 AT 1:18 PM (Merged)
Tiny
PLATINUMKANIKAS
  • MEMBER
  • 2 POSTS
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
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Sunday, December 13th, 2020 AT 1:18 PM (Merged)

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