P0174 and water throughout vacuum and intake lines

[jrandallc]

I'm fighting a P0174 code (at times it will throw both 0171 and 0174) along with poor performance, sluggish idle, etc. As I've been troubleshooting this, I've noticed at times there is water in different areas of the air or intake systems. I pulled the plastic tube from the bank 1 valve cover gasket where it enters the intake tube and it was wet at that hole. I also pulled the PCV elbow from the upper intake manifold and there was water on that tube.

Is this water a symptom of the cause of the P0174, or just a side effect of the problem that will go away once I fix the poor performance?

 

[RonD]

P0174(or P0171) means the computers calculations of the fuel to be added is low after the air/fuel mix has been burned.

Computer gets MAF(mass air flow) data and then calculates the fuel that needs to be added via the injectors to get the 14.7:1 Air:Fuel ratio needed in gasoline engines.
That mix is burned and then O2 sensor tells computer the Oxygen level in the exhaust.
Too little Oxygen means Rich, too much Oxygen means Lean.
If Lean computer adds more fuel until Oxygen level in exhaust is correct.
This takes milliseconds so engine is never really running Lean.

But computer lets driver know about the calculation errors by setting a code or codes.

If all the air coming into the engine is not going thru the MAF sensor then computer's calculation would be off, this is why vacuum leaks can set these Lean codes.

Water in vacuum lines wouldn't do it but will cause other issues, depending on where you live and local temp and humidity condensation in the PCV hoses can be normal.
Engine will be sucking in the air with water vapor(humidity) in it and so will the PCV system via the Vent hose.
When engine is shut off that water vapor will condense on parts that cool off first, like hoses, and if you remove those hoses you would see liquid water.
Like the water that forms on the outside of a cold beer glass on a hot day

There are 2 hoses for the DPFE sensor that go to the exhaust/EGR system, water in these hoses can ruin the DPFE sensor.
When gasoline(Hydrocarbon) is burned in the presence of air(oxygen) a normal by product is H2O(water), this is why exhaust systems rust from the inside out and why you often see water dripping from tail pipes.
Higher humidity would of course produce more water in the exhaust.

Having just one bank showing Lean code would tend to point to either failing O2 sensor on that bank of the engine or a lower intake vacuum leak on that side.
An exhaust leak on that side can suck in air(oxygen) making for a False lean on that O2 sensor.

If both banks get lean code then MAF sensor or upper intake vacuum leak would be indicated.
Both O2 sensors failing would be a long shot.
Clean MAF sensor.
After engine is warmed up and idling, unplug IAC Valve, idle should drop down to 500rpm or engine may even stall, either is good it means no vacuum leaks, if idle stays high then there is a leak.

 

[enjr44]

Is it water vapor or coolant?
A running engine makes water vapor (the white stuff you see coming out of the exhaust on cool mornings before things warm up). It is a by product of burning fuel. Once warm, it is still there, you just can't see it.

So some water/water vapor in the PVC system is normal on a cold engine. It should disappear when engine is warm enough to dry stuff out. And since the PVC system goes into the intake I think it could be evident there also.