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Old 01-12-2013, 02:09 PM   #1 (permalink)
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Default 2000 Taurus p0171, p0174

So I am working on my Grandmas Taurus. 70k miles, Grandpa serviced it regularly (every 2500 miles according to the maintenance log) before he passed.

It was running badly, couldn't idle, but would be fine at cursing speed.

Friday I finally got a check engine light 0171, 0174.

I tried the propane and cleaner tricks to find vac leaks, non found. I visually inspected all the lines, none are broken.

I pulled apart the pcv system, no cracks but replaced it all anyway.

I pulled the uim and lim and replaced those gaskets too.

Watching the live data on the car TPS has no dead spots, it is at .91 volts
Sucking on the EGR will kill the car.
Fuel pressure is right around 40 psi while idle.
IAC reads about 26% at idle.

B1S2 and B2S2 fuel trims are maxed out at all times
B1S1 and B2S1 fuel trims dance around 0%

When I rev the engine to 2500 rpm and watch B1S1/B2S1 the levels don't drop off, they just flatten out. I think that means I don't have any vac leaks.

Any help as to what I should test next would be appreciated.

I am out of ideas and codes are gone now, KOER finds no problems.

The idle is OK, but every once in a while it stumbles.

When I try to accelerate up to speed it just dies.

Last edited by fordjunky; 01-12-2013 at 05:21 PM. Reason: Current issues
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Old 01-12-2013, 05:21 PM   #2 (permalink)
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There is no problem, you fixed it. If both banks fuel trims are around 0% and the #2s (after converters) are consistently high voltage then that's the way it should be idling. Is it idling smoothly now?
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Old 01-12-2013, 05:36 PM   #3 (permalink)
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Thanks, I thought the 2s were a bad thing being high.

There is still a stumble on occasion at idle and it just dies when I accelerate. It takes a few cranks to get it to restart.
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Old 01-12-2013, 09:41 PM   #4 (permalink)
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Ignore the sensor 2 fuel trims. They aren't used for anything (null). Scan tool artifact.

If your total fuel trims (ST+LT) for each bank are 5% then you're in great shape.

When you snap the throttle does the fuel pressure go up, down, or stay constant?

IAC should be more like 30-35% at idle. Did grandpa mess with the idle base screw on the throttle body? Engine should still idle (about 500 RPM) with the IAC unplugged and all loads off (A/C, electrical, etc). There should be a slight gap around the edge of the throttle plate with the throttle completely closed. You should be able to stick a piece of paper in there without it catching.
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Old 01-12-2013, 10:31 PM   #5 (permalink)
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Might clean the maf sensor with CRC Mass Air Flow Cleaner (gray can) and maybe the iac too. May also check the fpr (fuel pressure regulator) if equipped. You replaced the pcv hose assy.? If still no success, I'd carefully recheck all of the vacuum lines behind the engine (firewall), vac. manifold box on the drivers firewall and under the throttle body.

Last edited by sheila; 01-12-2013 at 10:37 PM.
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Old 01-13-2013, 10:22 AM   #6 (permalink)
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When I start it cold, it revs and dies. If I feather the gas I can keep it running.

Fuel pressure goes up a little when I first hit the gas. but only by 1 psi or so. It stays pretty consistent while I am driving and accelerating and stopping.

When I got it to fall on its face this morning I was accelerating from a dead stop. The data shows the TPS jump but the IAC did not move. I was able to duplicate this 2 more times but then I could not duplicate it again and the car was running fine.

Maybe my IAC is on its way out?
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Old 01-13-2013, 10:31 AM   #7 (permalink)
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IAC does not need to move when you step on the gas. If the engine does not want to "go" as soon as you step on the gas it means you're not getting enough fuel or it's not registering the airflow (MAF) correctly.

I would check the fuel pressure during throttle snaps with an actual fuel pressure gauge in case the fuel pressure sensor is wrong. I would also try cleaning the MAF.

When you say it "dies" and "falls on its face" does the engine completely stop (you have to start it again) or is it just a hesitation?
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Old 01-13-2013, 10:34 AM   #8 (permalink)
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I will try it with a fuel pressure gauge.

Yeah when I say it dies, I have to restart the car.
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Old 01-13-2013, 12:03 PM   #9 (permalink)
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It's possible you may need to clean/replace iac. I just experienced the same symptoms on a 99tec and an iac swap remedied it. Are your air tube (hose) clamps snug?

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Old 01-13-2013, 02:22 PM   #10 (permalink)
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Had the same problem, IAC fixed it. I tried cleaning it but I ended up replacing it, it was full of carbon and hard to move.
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