Hoping the Ford doesn't have a DYING FUEL PUMP. We got. P0191, P0171, P0174.
Always learn that when you suspect a fuel delivery issue you start by changing the fuel filter. Yes I read up about fuel pressures.. On this car a mechanical gauge will tell you next to nothing since you need a scan tool to read the fuel pressure at the rail because of the returnless fuel delivery system that's on this model.
Here are some fuel pressures from the scan app. Fuel pressure sure gets a little low after its been running. Hoping a clogged fuel filter will yield relief.
I can replicate stumbles and stalls after it's driven a few hours, over the past few weeks.
Here,we can see the low fuel pressure, complete with CRAZY high STFT. Usually sets P0191 at this time, complete with stumbling, if given the chance. Taken after car turned off, I saw what I needed to see with fuel pressure dropping low (the tool measures it at the rail, like you're supposed to on this car.)
LTFTs being pegged at +25% started a few days ago. They go down with throttle, but, something doesn't seem right there. (I been keeping an eye on the oil level too, because fuel dilution. On it. Something is amiss but nothing that can't be solved.)
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Here it is, running idling about 20 minutes later, since I came back out to it after cutting open same car's old oil filter.
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Codes cleared, to see if they come back.
Fuel filter change won't hurt anything.
Clogged fuel filter, this is the original 18 year old one.... can mimic symptoms of bad fuel pump, so, hoping it is simple. Had me thinking O2 sensors, why misfires (you can feel them, they don't log or set codes,) etc. If not then okay yeah let's take a look at that fuel pump.
No idea what P0538 is. I know what P1000 is.
That's the latest.
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Here it is, idling in the driveway fully warmed up, before I go inside and eat breakfast and start my day. Been spending all night with the Taurus, reading the data.
My conclusion is.. change the fuel filter and go from there (re-assess.)
Note that fuel pressure is healthy now.
O2 values DO switch.. that's just that particular moment of screenshot. In case anyone was wondering.
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FWIW, according to this article, my fuel pump fits the description of dying.
https://batauto.com/threads/2004-ford-taurus-3-0l-vin-u-fuel-pressure-problems.6620/