Randomly shuts off, codes P0171 and P0174

SLPDYP23YRS

MEMBER
2001 FORD WINDSTAR
3.4L
V6
2WD
AUTOMATIC
110,000 MILES

My daughter's van listed above shuts off at any unforeseen time, (driving, slowing down, taking off). I'm trying to start with options that do not require new parts first. I had it shut off three times in five miles. Downhill grade to the left, uphill grade to the right, and slowing to a stop on level. The battery icon blinks before the engine shuts off. It did start while I put it in neutral still moving. Last night she stopped to buy groceries and it shut off. She tried seven times to keep it running, but each time it would run for a short time and then shut off. Replaced cracked vacuum line today. That cleared P0171 and P0174 codes. Shutting off problem started two days ago and continues after vacuum line replaced. EGR valve and coil pack replaced. Possibly low voltage from alternator? Wire harness to close to ignition module?

5 Replies

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

Hi,

Based on the codes and your description, it sounds like a fuel pressure issue or there are more vacuum leaks you are missing.

If you haven't already, check fuel pressure. I have a feeling it is going to be low. If you look at that attached pic, it is a portion of the diagnostics. It indicates a lean condition on both banks. So, either we have low fuel pressure, a false reading from the ECT, or there is another vacuum leak.

Recheck for other vacuum leaks. Here is a link you may find helpful:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Next, here is a link that shows how in general to test fuel pressure:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

________________________________

Because it is a lean mixture, I don't see it as a problem related to the ignition.

Here are the specs for the fuel pressure:

2001 Ford Truck Windstar V6-3.8L VIN 4
Pressure and Volume
Vehicle Powertrain Management Fuel Delivery and Air Induction Fuel Pump Fuel Pressure Specifications Pressure, Vacuum and Temperature Pressure and Volume
PRESSURE AND VOLUME
PRESSURE
Key ON Engine Running (KOER) .................... 28-45 psi (210-310 kPa)
Key ON Engine OFF (KOEO) .................... 35-45 psi (240-310 kPa)

FLOW
Flow Rate .................... 21 lbs/hr

__________________________________________________________

Let me know what you find or if you have other questions.

Take care,
Joe

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Friday, December 18th, 2020 AT 9:03 PM

SLPDYP23YRS

MEMBER
3 POSTS

Replacing the vacuum line cleared P0171 and P0174 codes and no other leaks found. What I have read about the engine shutting off at unexpected times warrants a different problem all together. Low voltage from alternator.

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Saturday, December 19th, 2020 AT 7:21 AM

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

Hi,

Yes, low voltage can create all kinds of issues. Have you checked voltage output from the alternator? Here is a link that shows how to do it:

https://www.2carpros.com/articles/how-to-check-a-car-alternator

As far as an ignition module, there isn't a traditional one on this vehicle. Since you are seeing the battery light before the problem happens, it is likely related.

One other thought is a failing crankshaft position sensor. Take a look through this link and let me know if it mirrors what you experience. However, I feel you are on the right track with the voltage issue.

https://www.2carpros.com/articles/symptoms-of-a-bad-crankshaft-sensor

Let me know your thoughts and if you have other questions.

Joe

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Saturday, December 19th, 2020 AT 2:49 PM

SLPDYP23YRS

MEMBER
3 POSTS

Voltage from alternator 14-15 vdc. AutoZone rep said battery checked bad and was replaced with new. Car shut off again without warning. No error codes involved. With all the new parts it runs like a top until it shuts off, but starts up again. Crankshaft positioning sensor seems to be the next possibility? It's getting costly to replace parts that may not be bad. Any additional thoughts?

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Wednesday, December 23rd, 2020 AT 3:14 PM

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

Hi,

Have you been able to check fuel pressure? Also, if the vehicle fails to start, we have two ways to check the crank sensor. First requires a live data scan tool. Check to see if there is an RPM signal. Or, check to see if you lost spark to the plugs. Actually, if there is a tachometer in the vehicle, it should move a bit when cranking.

https://www.2carpros.com/articles/how-to-test-an-ignition-system

Let me know. I don't want to see you replace it and have the same problem.

Let me know.
Joe