• April 4, 2016 at 1:37 pm

    Any one have any idea’s why I would get P0171 and P0174 codes on my Speedster. They are to lean on bank 1 and bank 2 . Have replaced 02 sensors and did not help the problem and get evap not ready in IM’s Have looked all over everything for hoses off or something oblivious but everything seems alright. Any help will be greatly appreciated. Thanks


  • April 4, 2016 at 1:51 pm

    Evap codes are usually related to the gas cap, try replacing that if yours has a cap. I’ve been getting the P0174 error recently myself. I usually get it after I wash my car and it gets wet inside cap area, but mine is a 2010 and does not have a cap so I’m not sure how to resolve the issue. Pain in the ass. In my opinion not one of Fords better ideas.

    • This reply was modified 1 year, 8 months ago by Profile photo of Jay Jay.
  • April 4, 2016 at 3:24 pm

    Thanks Jay will try a new cap not much to lose after swapping 02 ‘s out .


  • April 4, 2016 at 5:31 pm

    Did you change anything prior to the throttle body? New filter, cold air kit, new MAF or MAF tube? Check all your connections from the air cleaner forward?

    08 Stage 3 Roush, Vista Blue coupe. "made the Kessel Run in less than twelve parsecs".
    08 Trak Pak Black w/red stripes #97

  • April 4, 2016 at 8:16 pm

    No did not change anything prior to the light coming on .Changed the 02″s hoping that maybe that was it since it only has 37000 miles on it and sits a lot of the time. Was coming back from Pensacola when it came on . Had got gas a couple hours before and stopped and when I cranked it back up it came on. Today did clean the air tube and mass air sensor. checked for vacuum leaks and replaced gas cap . The evap is working now but still got the P0174 and P0171 is pending. Have not drove it but about 14 miles since doing that and light came back on telling the p0174 and p0171 was pending . Thanks Ken don’t really know but will try to check fuel pressure and maybe replace fuel filter it can’t hurt . The car runs really good no bucks skips misfires .it does not even have hot exhaust or smell funny like it would be lean so am trying all the little things use to do on the ob1 stuff.


  • April 4, 2016 at 9:07 pm

    Sorry. I have to ask but, did you clear the codes?

  • April 4, 2016 at 11:26 pm

    I figured someone would ask after I left and Rich I did but it was worth the asking I will try to do better, Thank you


  • April 6, 2016 at 1:24 pm

    yes I would start with checking the fuel pressure and maybe replacing the fuel filter. Did you look to see if there are any TSB’s for this code?

    Do you have a handheld tuner so you can datalog ?

    • This reply was modified 1 year, 8 months ago by Profile photo of Ken #1705 Ken #1705.

    08 Stage 3 Roush, Vista Blue coupe. "made the Kessel Run in less than twelve parsecs".
    08 Trak Pak Black w/red stripes #97

  • January 8, 2017 at 12:07 pm

    I am having the same problem and the same codes with my 2006 Mustang GT with the Roushcharger system on it.On my car the problem was a stumble after startup. This would only happen after the car was hot and after being shut off for 20 minutes say to run into a store. After startup it would stumble RPMs would drop and sometimes the engine would die. stumble would usually correct itself in about eight seconds, but very frustrating having to deal with a car that would barely stay running after startup. My problem still has not been solved and it seems like I have been chasing it for years.
    P0171 and P0174.
    Rudy, if you find a solution please share here. I have taken the car in twice First time was to an independent repair shop where the only possible problem they could see would be dirty fuel injectors.I changed the fuel injectors and had no difference. In my research I have changed the fuel pump fuel filter MAF sensor.No vacuum leaks were found by me or that shop I took the car to. Then six months ago I took the car to a Ford dealership with an extensive write-up of the work I had done and the diagnosis from the Independent shop. To my surprise, the tech at Ford moved the MAF sensor from the air tube in the Roush kit to the air box That the MAF sensor came stock in the Mustang. That fixed all the problems for a few months and I was really thinking this problem was gone for good, but now the very same symptoms have come back again, exactly like before just as if no action had been taken to repair it. If I have been driving the car around for a while and have to run into a store, I know when I come back out to start it it is going to stumble and probably die.And I am wondering if I should take the car back to Ford again for another diagnosis.

    • This reply was modified 11 months, 1 week ago by Profile photo of John John.
    • This reply was modified 11 months, 1 week ago by Profile photo of John John.
  • January 9, 2017 at 9:41 am

    Changed the gas cap and solved the code problems. Mine never did run bad just kept popping the codes Sounds more like a vapor lock problem . I know they say fuel injected cars don’t have this problem but also seen on tv yesterday where if the return on a fuel injected car is not working right it will let the fuel heat up because of being compressed by the pump pressure and no where to go and cause a vapor lock . Not saying that is your problem saying they can vapor lock. Wish you luck on finding the problem and please post what your problem turns out to be and the cure in case others have the same .. Thanks Rudy