"Pending" P0171 and P0174 code and PCV question

[ashner19]

Hi, I have a 2001 Sport v6 sohc and after a week out of town not starting the explorer i see the check engine light on. Got the lean codes and checked this forum. Went ahead and disconnected the battery then checked hoses, cleaned MAF sensor, replaced air filter, and put a new gas cap on. Check engine light went away and after testing again I get both codes as "pending" this time. Cleared the codes and tested again and now I get just the P0174 code as "pending". Should I worry about pending codes and try to get them cleared/issue resolved or is this not a big deal?

Truck runs fine but sometimes starts rough on cold starts. Replaced the fuel filter about 3 years ago and figure I should again since its cheap. Replaced the IAC a couple of years ago but didnt get a new gasket. Will clean IAC next and get a new gasket for it. I found my pcv valve and would like to check/clean but am having a hard time removing it. Its in a tight spot and I dont want to damage any hoses back there. Can I spray maf cleaner or pb blaster back there to loosen the pcv?

Any advice or suggestions for how to remove the pcv and if I should even care about pending lean codes would be appreciated.

 

[donalds]

This sounds like classic upper and lower intake gaskets

 

[ashner19]

This sounds like classic upper and lower intake gaskets

Not the job I was hoping to tackle

 

[swshawaii]

Check the PCV elbow IF you have a Job 2 engine.
P0171 & P0174 4.0L SOHC's Sport/Sport Trac

 

[donalds]

It's not that bad

 

[donalds]

Yes a pic of your engine bay would say a thousand words

 

[German Engineer]

Before you just go ahead and replace any intake manifold gaskets I'd try checking thoroughly for vacuum leaks first.
There's about half a million vacuum hoses running around all over the engine bay. It's awfully easy to miss one somewhere.

And I'd also hook up a fuel pressure gauge as well to check if it's not a problem with fuel supply that causes the lean codes. (Low fuel pressure because of a weak fuel pump was the reason for those lean codes on my OHV engine some years ago for example.)

If you can, then hook up an OBD2 scanner and look at the fuel trim values in live data.
If it's a vacuum leak the fuel trim will usually be affected mostly when the engine is running at idle and not so much when running under maximum load at full throttle.

The OBD2 live data should also be able to give you a general idea if the O2 sensors are still working good or if they're sluggish.

Another super simple check you can do is to detach the big intake hose, let the engine run idle and then plug the hole(s) in the big throttle body valve with your finger, to block air from getting in through there.
If that doesn't suffocate the engine and make it die off quickly, then you'll most certainly have a (somewhat bigger) vacuum leak somewhere.
Sadly this simple check won't tell you if there's a smaller vacuum leak somewhere or not, so in your case with just pending codes after you cleared them, I'd expect the engine to die off. But it's such a simple and quick thing to try, it's pretty much always worth checking.

Too much (unmeasured) air, not enough fuel, or bad sensors, all those things can trigger lean codes for both banks simultaneously, not just a pair of bad intake manifold gaskets.

 

[ashner19]

Thanks for the quick responses guys! I have a Job 1 engine with 185k miles. No major problems at the moment but want to stay ahead of anything i can. I will continue to check vacuum hoses and check fuel pressure when i replace the fuel filter. Going to check the fuel trim values now.

 

[Mr. Alligator]

These engines do not like unmetered air, regardless of the source.

Good luck.

 

[1sicbronconut]

Thanks for the quick responses guys! I have a Job 1 engine with 185k miles. No major problems at the moment but want to stay ahead of anything i can. I will continue to check vacuum hoses and check fuel pressure when i replace the fuel filter. Going to check the fuel trim values now.

Since you seem to have something to monitor fuel trims, you'll want to look at short fuel trim and while watching these spray some brake cleaner around the base of the intake manifold and see if the trims change good test for intake gaskets.