2002 expedition stalls and has P0171 and P0174 codes
 

My check engine soon light is on with error codes P0171 and P0174 (left side is what they told me). It now stalls or dies at stop signs, lights or pulling into parking spaces if I don't keep gas pumping to it. It's much much worse on days below 40 degrees. Has anyone had the same problems or have any ideas on simple fixes without taking it to a shop?
Thank you

Yep. Find the vacuum leak.
Typically in the PVC system.

OTOH, could be a dirty MAF,
or fuel supply issue.

Look at the Freeze Fram data to see
when the fault occurred. If it happened
under light throttle, look for vacuum leak.
If it occurred under heavy throttle look
for fuel supply issues.

Since you are having idle (light throttle) problem,
My money is on the vacuum issue.

Thank you! I will start there!

A vacuum leak big enough to cause a stall should be pretty easy to spot. Take a spray can of carb cleaner and spray around suspected hoses and you should be able to hear a change in the engine. Especially that big vacuum pipe at the rear of the intake manifold. The rubber elbow on that thing is notorious for cracking. Dorman makes a replacement for that piece. The other little elbows and vacuum hoses all seem to rot out in time. You can find the complete PCV vacuum tree, which includes that rear elbow, on Amazon for about $65 if you end up needing the whole line. You can find most any of those pieces on Amazon if you know the part number.


-Mike

Take a look at your PCV hose on top of the passenger side valve cover and follow it around to the back of the intake to verify which one you have. See below........

https://www.rockauto.com/en/moreinfo...385333&jsn=451

You can also find a Dorman one for cheaper. I got a Motorcraft from my local dealer for $36.

I had the same codes on my truck and it had started surging and occasionally stalling. Started off minor in the fall but got worse as the temps dropped heading into winter. Like people said above, i changed the PCV system but no change. Ended up being the intake manifold gasket, which is a common problem from what i've been hearing.

Stalling issue.
 

My Navigator does the same thing. I've changed the pcv, and intake gaskets to no avail. It will run fine for a while and then at random just stall out. P0171&P0174 codes are back after clearing the codes about a week and a half ago. I'm at a loss as to what to do to fix this issue as this is my main source of transportation

Check the fuel pressure at the fuel rail, should be 50-60 psi. Then check for vacuum leaks with a smoke machine. It'll show any leaks within about 15 seconds. You'll need a compressor, or tank of compressed air to run the smoke machine.

-Mike



Mechanic's Smoke Generator