Hey group thought I would post this fix. I’ve been having the 71/74 codes for some time. I sprayed all the known culprits with brake cleaner and found the two connections on top of the manifold leaking. Put some silicone on them and the leak stopped but the codes still kept coming back. So parked the car and decided to take it in. Just got it back today and had a great conversation the the mechanic. Took him a day and a half to find it so I don’t feel so bad. Picture shows the line coming off the bellows (screw driver). Come to find out this goes to the rear valve cover, I tried to find a diagram as the coil pack hides it from view. This had become twisted and loose from the valve cover. He was able to get it re-inserted with out removing the plenum and all is well, both short term and long term fuel trims are now right within spec. He did say if the problem returns the grommet on the valve cover will need to be changed. I’m thinking about removing the fuel injectors and having them cleaned and rebuilt so it will happen then. Hope this helps someone.
Jon

 

I’ve been struggling with these 2 codes. Numerous fixes. Keeps comin back

 

John. Can u confirm that this fix solved your P0171-0174 code problems please ?

 

Yes, I have put about 100 miles on the car and no codes. When I was chasing this I would clear the LTFT’s and then watch them climb just at idle until they maxed at around 19% and set both codes. Since this repair I have done the same test and the STFT and LTFT’s stay right where they should be. I will edit this in a bit with a picture of my scanner.

 

Almost any OBD tool with live data e.g. elm327 should be good enough for that