2000 Ford Windstar 3.8 P0171 P0174

Vehicle had fault codes for lean fuel system, both banks.

This indicates a problem affecting the entire engine.

With fuel trim faults, freeze frame data is a great starting point. Freeze frame data indicates fault codes set at idle.

Monitoring fuel trim during a test drive confirmed the vehicle was lean at idle. Note the graphs below indicate lean at idle. Once the engine RPM is raised from idle to 2500 rpm (in PARK) the fuel system is no longer lean. A vacuum leak can be detected this was. As the amount of unmetered air is larger (or comparable) compared to metered air. Once the RPM is raised the metered air amount becomes greater than the unmetered amount (vacuum leak).

After this I spoke to the mechanic who was working on the Windstar. He stated the same fault codes were present last month. He found a leaking intake manifold and a TSB. Therefore he replaced the front valve cover and intake manifold profile gaskets.


I quickly checked over his work. Everything looked in place. The only spot that propane could influence fuel control was at the intake manifold runner control bushing. I found this to be normal as all 3.8 intakes will have some level of leak here. New lower intake manifold does not remedy the leak.

I looked over the TSB and asked if he performed a needed PCM updated. They had not.

Next up I reprogrammed the PCM.

After the PCM software update I test drove the vehicle and confirmed it was now in proper fuel control. A second test drive confirmed the same result with no fault codes.

The shop was half way there. They performed almost all the needed repairs. A simple software update and they were done. With computers controlling almmost every function on late model vehicles it is always smart to check if software levels are up to date when performing repairs.

8 thoughts on “2000 Ford Windstar 3.8 P0171 P0174

  1. I am dealing with a similar situation. I am curious what symptoms the Windstar was experiencing. Mine will randomly stall at idle or downshifting situations with foot off the accelerator and then will reluctantly restart. It also loses acceleration power around 2500+ rpm’s. Of course, the standard p0171 and 4 codes were in the system and the MIL has been on no matter how many times I reset it.

    I first noticed the IMRC rods were not connected due to dryrotten retainers. I replaced those with ford parts.

    I still had the same drivability problems so I removed the upper and lower intake and resealed everything. the problem was greatly reduced but still prominent at random intervals.

    I have a very significant leak where the intake runner shafts enter into the lower intake manifold and I’m trying to figure out a way to reduce that.

    Any ideas?

  2. @tim

    I would check your software level. Unless you have the update that remedies this issue it is silly to continue chasing the issue.

    Perform the PCM update, if that doesn’t fix it take a look at your fuel trim at idle, 2500 rpm in park and at a steady cruise. This will give you an indicator as to when the problem is present.

    There is also a TSB describing how to check your MAF sensor using the inferred baro reading.


  3. Hello! I know this is old but figured I’d give it a shot- I have the exact same issue and am sure I have an isolator bolt problem. If I spray throttle cleaner at the front bottom of the intake, my fuel trims go crazy. I called Ford to see about a ECM re-flash as you described above in this article but they know nothing about it. Can you tell me how I might further diag if I just need a computer re-flash? thank you! shawn.

  4. Shawn, There are updated gaskets and bolts (a kit from Ford) to reseal you intake manifold. I would look into those items.

    I would be careful using throttle cleaner on a running engine. You could create a fire. If the fuel trim numbers are displaying a lean condition at idle only, and your testing shows fuel trim responds to an intake manifold area richening, I would guess you are pretty safe resealing the intake. After the reseal, I would suggest the ECM update if it hasn’t been done. A shop with re-flash ability will be able to tell you if your ECM has the latest software.

  5. I called the local Ford dealership and they said they would charge me an hour of labor ($112) to check the software version on the computer. If it needs to be updated, they will update it as part of that same price. However, if it doesn’t need to be updated, I’d still be out the $112.

    That seems like a complete rip-off to me.

    Any suggestions on how to get this software version checked at a good price? Seems like Ford should be willing to check the software version for free – I’m guessing all they need to do is plug in a scanner and it will tell them the software version. Is that right?

    A local independent shop said they would check the version for me for $40, but then if it needed to be updated it would be another $85 and they would need to take the car to another place to have the computer software updated – I am guessing they just take it to the dealer…

  6. If your PCM was updated, there should be a label on the PCM. The label will be a white sticker with the latest version hand written.

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