Misfire and lean problem
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Misfire and lean problem
So i bought a 2007 f150 with a 5.4 in it with 100,000 miles on it a little less than a year ago. Everything has been great up until now, the check engine light came on, so i took it to get the code read and it read a p301 and a p171. I did some research and figured that it was running lean as well as had a cylinder 1 misfire so i replaced the plugs first, codes still remained. So i changed the cop on cylinder 1 and it still had the same codes so i finally changed the fuel injector and a whole new set of codes came up ( p351,171) so i am just tired of throwing parts at it and was wondering if anyone has had a similar problem or if anyone has any recommendations?
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Joined: Jul 2005
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the P0351 normally means the injector wire was not plugged into #1 cylinder or the pins are bent on the plug... its not making contact ........ the P0171 means you have a lean mixture on bank #1. Could be due to #1 injector not injecting fuel on that side.............normally 0171 goes with 0174, ( since you did not get 0174 also ) and you would guess vacuum leak due to bad hoses... but in your case, probably bad injector wire / plug is causing the problem.
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Joined: Jan 2015
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From: San Antonio, Texas
@Steve(ill) is RIGHT - but for the wrong reason.
The whole problem can be explained by the P0351 code, which is a bad wire - but on the 'primary side of the COP' instead of the injector (which would be a 0201). The PCM is smart enough (clever little *******) to know that if the coil 'primary' is open it cannot make the spark plug SPARK. So the injector on that cylinder is shut down as a precaution to the CAT as long as that condition persists. But THAT cylinder is still pumping oxygen into the exhaust - which is sensed by the O2 sensor. So fuel is ADDED to the other three cylinders due to the 'lean' condition.
The P0171 code pops up when 'fuel trims' on that bank exceed 25% long term and 10% short term. If EVERYTHING else was perfect - one cylinder would only be 25%, but your fuel trims might have been a little bit elevated because of other aging conditions. So the P0351 (bad connection to COP) was the start of problems, lead to the 'apparrent' lean condition because injector #1 is shut down by the PCM.
Start by getting rid of the P0351 and see what happens.
The whole problem can be explained by the P0351 code, which is a bad wire - but on the 'primary side of the COP' instead of the injector (which would be a 0201). The PCM is smart enough (clever little *******) to know that if the coil 'primary' is open it cannot make the spark plug SPARK. So the injector on that cylinder is shut down as a precaution to the CAT as long as that condition persists. But THAT cylinder is still pumping oxygen into the exhaust - which is sensed by the O2 sensor. So fuel is ADDED to the other three cylinders due to the 'lean' condition.
The P0171 code pops up when 'fuel trims' on that bank exceed 25% long term and 10% short term. If EVERYTHING else was perfect - one cylinder would only be 25%, but your fuel trims might have been a little bit elevated because of other aging conditions. So the P0351 (bad connection to COP) was the start of problems, lead to the 'apparrent' lean condition because injector #1 is shut down by the PCM.
Start by getting rid of the P0351 and see what happens.
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Joined: Jan 2015
Posts: 1,083
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From: San Antonio, Texas
Thanks @pdqford.
See, I have NEVER forgotten the lessen I learned from YOU by trying to prove you wrong a long time ago - when I set up my Torque Pro app to monitor fuel trims and O2 sensors while I went and 'un-pluged' a COP to prove what fuel trims would do --- I THOUGHT!
See, I am capable of learning, even at my 'ripe' old age.
Cheers
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