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Engine running rich at idle in closed loop

Tiny
AARON N
  • MEMBER
  • 2002 FORD TAURUS
  • 3.0L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 82,000 MILES
All new gaskets on top of motor, MAP-EGR-injectors-plugs-coil, many new parts. Can't find any major vacuum leaks. Had to pull all 4 new 02 sensors black with soot. Good power when driving on an open road, but when engine is warmed up put in park, surges at idle. 1132- 1152 bank one and two rich. Don't know what to do!
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Thursday, January 6th, 2022 AT 12:33 PM

13 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

High fuel pressure can cause a rich mixture. Have you checked fuel pressure to see if it is within the manufacturer's specifications? If not, I would start there. Here is a link showing how in general it's done:

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

Next, a faulty coolant temperature sensor can also cause this type of issue. The vehicle's computer (PCM) receives a signal from the CTS indicating coolant temperature. If the sensor indicates it is -40 degrees below 0, the PCM will dump fuel to allow the engine to run in extreme conditions such as this. However, the PCM doesn't realize the sensor is wrong and doesn't set a code.

So, if you have a live data scan tool, before starting the engine, see what the signal from the ECT is. It should be really close to ambient temperature. You may want to inspect the connector at the ECT sensor and inspect it for corrosion, damage, or a bad connector. I attached 2 pics below showing the sensor location.

Let me know what you find.

Joe

See pics below.
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Thursday, January 6th, 2022 AT 5:27 PM
Tiny
AARON N
  • MEMBER
  • 7 POSTS
Funny the coolant sensor was only thing left not replaced, did lower one when doing intake still surging when in closed loop, don't know what to do. Fuel pressure 40. Thanks for your help. Cats?
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Saturday, January 8th, 2022 AT 2:28 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Did you replace the temperature sensor? If you did, have you done a leak-down test on fuel pressure? You may have an injector leaking.

Basically, a leak down is when the pump is turned off. Pressure will drop a little but should take a little time and shouldn't happen really fast.

Let me know.

Joe
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Saturday, January 8th, 2022 AT 11:30 PM
Tiny
AARON N
  • MEMBER
  • 7 POSTS
Yes, put in new coolant sensor, no change, fuel pressure is 39 to 40 at idle to highway speed with live data. But I did find muffler may be plugged hotter in front than in back. Original muffler is 20 years old. New one on its way! I will let you know. Thanks, Aaron.
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Sunday, January 9th, 2022 AT 6:13 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

Is it possible for you to provide me with the short-term fuel trims? Fuel pressure is good, and a vacuum leak won't cause a rich mixture. Also, let me know if you have checked the catalytic converters. As far as the muffler is possible, so let me know what you find.

Take care,

Joe
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Monday, January 10th, 2022 AT 3:10 PM
Tiny
AARON N
  • MEMBER
  • 7 POSTS
Joe, took some time to get this done but the rear cat is on the garage floor plugged 90% I thought it was muffler wrong. I really missed it on this one, the end is near. Will give final report when done. Thanks, Aaron
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Friday, January 14th, 2022 AT 6:01 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

I had a feeling if it was exhaust related, it would be the converter. However, when you mentioned the muffler, I was thinking anything is possible.

Thanks for the update. It's appreciated. Let me know how things turn out for you.

Joe
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Friday, January 14th, 2022 AT 9:15 PM
Tiny
AARON N
  • MEMBER
  • 7 POSTS
This is not going well, the rear cat was plugged so I replaced it, engine still surging. All that`s left is the fuel system, fuel pump- fuel regulator? Has new injectors, fuel filter looked original when I replaced it. Fuel pressure is always 39 to 40 on live data, fuel pressure gauge won`t fit orifice on fuel rail. The upstream 02`s are at 1mv. Not switching. Any input I would be grateful again. Thanks Joe.
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Wednesday, January 19th, 2022 AT 12:46 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

If the 02 sensors aren't switching, chances are either they are bad, there is too much resistance in the wiring, or there is an issue at the connector. If it was a downstream sensor, I would say the converter isn't working properly and there is little to no change in oxygen level readings

These are new sensors, correct?

Let me know.

Joe
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Wednesday, January 19th, 2022 AT 1:59 PM
Tiny
AARON N
  • MEMBER
  • 7 POSTS
Yes, o2`s are new, all four.
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Wednesday, January 19th, 2022 AT 3:57 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
With your scan tool or a voltmeter, try this test and let me know if you see voltage changes from the sensor.

https://www.2carpros.com/articles/how-to-test-an-oxygen-sensor-02-sensor

If you have already done this, let me know. Also, let me know any specific codes you have retrieved since the exhaust work.

Joe
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Wednesday, January 19th, 2022 AT 6:15 PM
Tiny
AARON N
  • MEMBER
  • 7 POSTS
Subzero weather making it slow going, found fuel pressure and gauge fitting to work on ford fuel rail, 30 PSI. Pull off vacuum line from fuel pressure sensor goes up to 39 put back on back to 30. Bad fuel pump? Live data said 40 all the time, that's why I never checked the fuel rail. This has to be it! Thanks again for your input.
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Wednesday, January 26th, 2022 AT 10:25 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

It's on the low end, but still within spec. The manual gauge is usually 5 to 7 PSI lower than a scan tool.

Have you ever checked the short-term fuel trims? I mentioned it right before you noticed the converter issue.

Let me know,

Joe
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Wednesday, January 26th, 2022 AT 5:01 PM

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