I would be looking for vacuum leaks, look very carefully at the intake hose that connects the throttle body to the airbox, they crack and cause all sorts of problems.

Could also be a fuel pump on the way out as well.

 

That main hose between the airbox and TB has been replaced.
Vacuum lines have been checked and replaced as needed.
Any other ways to see if it's the fuel pump?

Don't really want to begin just throwing parts at it.....

Thank You

 

Next time it wont start hot, try cranking with the throttle wide open (accelerator pedal to the floor)

Generally the P0174 is a vacuum leak but could be other things.

My local Mazda dealer will do a diagnostic for $125. I took them a problem that took them several hours to diagnose and saved me quite a bit of hassle. Just a thought.

 

Thank You for the attachment.

I not only cleaned the MAF, which changed nothing; I swapped it with the MAF out of my '13 6. The '13 still runs fine with the MAF from the '05, the '05 with the '13 MAF still has the issue.

Thank You

 

This will not be easy to diagnose, but in my experience, when either the fuel pressure regulator or the pump itself is failing, you get warm start issues. It could be a weak spark too, but I find it very unlikely that all 6 coils get weak at once, almost impossible. You need to check fuel pressure and leak down of the fuel system. I do not know the specs, but the fuel system is supposed to hold near full pressure when you turn the engine off. Hopefully someone here has the leakdown/pressure specs.

 

P0174 is for too lean on bank 2......front cylinders. So.....can't you eliminate anything that would affect both front and rear cylinder banks? such as fuel pump or air box connecting hose. for the record.....i have been having very similar issue(s). no success yet in determining what the cause is. it just might be 2 separate issues. with one being the hard start when warm....and another being the 'too lean' P0174 code. my car will only trigger the P0174 code occasionally. And it is usually when i am cruising along with nothing eventful really happening. always surprises when the check engine light comes on.....because i feel no change in performance or anything. i will let you know if/when i do find something. good luck.

 

I am also facing the same issue with my 05 mazda 6. If you have solved this issue by now, can you help me how can I do the same?

 

Did you guys solved the issue?