So I bought my X Type earlier this year and the CEL came on immediately. Foolishly, I did not run the OBD scanner because the deal seemed so good. Anyway, P0171, P0174, I replaced the MAF, Filter, Brake Booster Hose, IMT O-Rings, gave it a BG 44K and the Breather hose was replaced before I got it so it is the new type. It stopped throwing codes for like a week, it passed inspection and everything seemed okay. BTW thanks to all the previous posts on this subject that got me to pass inspection. Unfortunately, its gotten colder and the code P0174 pops up every once in a while. What could it be. Is it due to cold start ups? If I let it warm up I don't usually get it.

 

Chip: You've done all the right repairs so far. A small vacuum leak is probably causing the P0174 code - lean condition on bank 2, the 3 cylinders on the radiator-side. As the weather gets cold, rubber becomes stiff and doesn't seal as well, and cold air is more dense so more can squeeze thru the leak.

You've fixed three of the top five vacuum leaks:
1) Brake booster hose. Check connector into the top of the intake manifold to be sure it's not loose

2) IMT O-rings

3) PCV breather hose. Should have metal band clamps to ensure a good seal on both ends

A few more things to check:

4) As you do these repairs, reset the ECM so it more quickly relearns how to optimize engine parameters, e.g., fuel trim, spark timing, throttle position. With the ignition key removed, disconnect the positive cable from the battery post and hold it momentarily against the negative post. Then reconnect the positive cable to the positive battery post and drive as you normally would while the ECM re-learns the best operating conditions.

5) The black, ~3 inch, ribbed hose between the air filter / MAF sensor and throttle body: Sometimes it splits on the bottom due to engine heat & age. Also confirm it has metal band clamps on both ends

6) PCV valve: When old, these sometimes stays open too long, allowing too much crankcase air into the intake manifold. Hard to tell, but easy to replace for less then $15 and 15 minutes.

7) Double check all vacuum lines into the intake manifold. Sometimes a former owner / mechanic will break a connector and attempt to glue it together with RTV silicone.

8) The intake manifold gaskets. Normally I replace these only when it's time to replace the spark plugs, or if the engine is misfiring and I need to check the coils or look for oil in the spark plug wells on bank 1 - the firewall side.

A few more suggestions:

a) If you scanner displays fuel trims, we can show you how to confirm that the root cause is a vacuum leak. If 'no', consider getting an ELM327 scanner for less than $15 and an free iPhone or Android app that will display the fuel trims.

b) Smoke test: Google the internet for several do-it-yourself smoke test videos, or have a mechanic do it for you.

c) Leak tests with carb cleaner, starter fluid or propane: Again, Google the internet for videos, or again, have a mechanic do it.

Let us know what you find and we'll help you from there.

 

Thanks for the help, I'm at work now but I will try and take a look when I get home. The cold air vs stiff rubber seals seams like it makes a lot of sense.

 

I suffered same issues, basic the same story, passed inspection after repairs etc.
Had the code come back a few times in the months since but it always went away.
Now it has been gone for months so not dug into it as the chances of causing more issues is always on my mind.
My intake gaskets were one of the first things replaced, so not the cause for me but I would go there next if it is bugging you, fairly cheap and easy maintenance to do. And on top of that you will have most every common issue apart in the process of replacing them and you can give it all a good inspection and just may come across something.

I have also heard of a dirty fuel filter as a cause. less fuel, more air, o2 reads it as a lean condition? not sure myself