09 focus see p0171
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A lean fuel condition may exist if the engine is sucking in too much air and/or the fuel system is not delivering enough fuel. If bad enough, a lean fuel condition may cause lean misfire, a rough idle, hesitation or stumble when accelerating, and/or poor engine performance.
Unmetered air can enter the engine through a vacuum leak, a dirty mass-airflow sensor that is not reading airflow accurately, an EGR valve is not closing and is leaking exhaust into the intake manifold, an EGR valve that is allowing too much flow (because the EGR differential pressure sensor that monitors EGR flow is faulty and is under-reporting EGR flow). This is called the DPFE sensor and they are very common to go around the 60,000 mile mark.
If the problem is not enough fuel, the underling cause may be a weak fuel pump, restricted fuel filter, leaky fuel pressure regulator or dirty fuel injectors. It could also be a sticking idle control motor but that wouldn't cause a lean condition most of the time. It would just cause a poor idle.
The reason is may be more of a problem when the A/C is on is because the compressor puts additional load on the engine.
Are they original oxygen sensors? When was the last tune-up?
Unmetered air can enter the engine through a vacuum leak, a dirty mass-airflow sensor that is not reading airflow accurately, an EGR valve is not closing and is leaking exhaust into the intake manifold, an EGR valve that is allowing too much flow (because the EGR differential pressure sensor that monitors EGR flow is faulty and is under-reporting EGR flow). This is called the DPFE sensor and they are very common to go around the 60,000 mile mark.
If the problem is not enough fuel, the underling cause may be a weak fuel pump, restricted fuel filter, leaky fuel pressure regulator or dirty fuel injectors. It could also be a sticking idle control motor but that wouldn't cause a lean condition most of the time. It would just cause a poor idle.
The reason is may be more of a problem when the A/C is on is because the compressor puts additional load on the engine.
Are they original oxygen sensors? When was the last tune-up?
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Tune-up was done about 15,000 miles ago. O2 sensors are original there's no easy way to check the fuel pressure on this thing it doesn't have a Schrader valve. And there is no fuel filter it just has the sock on the pump. I've sprayed the vacuum lines intake manifold everything and I don't see or hear any vacuum leaks.
I'll bet you it's the DPFE then. They are common. I replaced a bunch of them in the past on Fords.
OVERKILL
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Originally Posted by StevieC
I'll bet you it's the DPFE then. They are common. I replaced a bunch of them in the past on Fords.
This. This failed on ours and caused all kinds of funky drivability issues. It's also insanely common. There's a bypass trick for it that will allow you to confirm it as the culprit.
I'll bet you it's the DPFE then. They are common. I replaced a bunch of them in the past on Fords.
This. This failed on ours and caused all kinds of funky drivability issues. It's also insanely common. There's a bypass trick for it that will allow you to confirm it as the culprit.
OVERKILL
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Looks like this:
![[Linked Image]](https://www.rockauto.com/info/48/F77Z9J460AB-FRO__ra_p.jpg "[Linked Image]")
A 2009 Focus does not have a DPFE like older models. It is built into the EGR valve.
OVERKILL
$100 Site Donor 2021
Originally Posted by bdcardinal
A 2009 Focus does not have a DPFE like older models. It is built into the EGR valve.
Odd, it shows up under the 2009 2.0L I4 on RockAuto
https://www.rockauto.com/en/catalog/ford,2009,focus,2.0l+l4,1443428,emission,egr+pressure+feedback+(dpfe)+sensor,5088
A 2009 Focus does not have a DPFE like older models. It is built into the EGR valve.
Odd, it shows up under the 2009 2.0L I4 on RockAuto
https://www.rockauto.com/en/catalog/ford,2009,focus,2.0l+l4,1443428,emission,egr+pressure+feedback+(dpfe)+sensor,5088
Originally Posted by OVERKILL
Originally Posted by bdcardinal
A 2009 Focus does not have a DPFE like older models. It is built into the EGR valve.
Odd, it shows up under the 2009 2.0L I4 on RockAuto
https://www.rockauto.com/en/catalog/ford,2009,focus,2.0l+l4,1443428,emission,egr+pressure+feedback+(dpfe)+sensor,5088
The Ford catalog does not list one. I have seen tons of errors in RockAuto's listings.
Originally Posted by bdcardinal
A 2009 Focus does not have a DPFE like older models. It is built into the EGR valve.
Odd, it shows up under the 2009 2.0L I4 on RockAuto
https://www.rockauto.com/en/catalog/ford,2009,focus,2.0l+l4,1443428,emission,egr+pressure+feedback+(dpfe)+sensor,5088
The Ford catalog does not list one. I have seen tons of errors in RockAuto's listings.
It has one it's just built into your EGR valve which means you get to replace the whole EGR if it's the culprit. The reason the A/C compressor would cause this code is because the EGR is reporting false value to the PCM and so it's actually running a tad lean continuously by not fully closing the EGR valve, but it's not lean enough to cause the code and then when the engine is put under extra load from the A/C compressor it pushes it over this threshold and causes the lean condition and the PCM stores the trouble code.
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OVERKILL
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Originally Posted by StevieC
It has one it's just built into your EGR valve which means you get to replace the whole EGR if it's the culprit. The reason the A/C compressor would cause this code is because the EGR is reporting false value to the PCM and so it's actually running a tad lean continuously by not fully closing the EGR valve, but it's not lean enough to cause the code and then when the engine is put under extra load from the A/C compressor it pushes it over this threshold and causes the lean condition and the PCM stores the trouble code.
Be interested in seeing the results of giving the EGR valve a few light taps with a wooden or rubber mallet and disconnecting it.
It has one it's just built into your EGR valve which means you get to replace the whole EGR if it's the culprit. The reason the A/C compressor would cause this code is because the EGR is reporting false value to the PCM and so it's actually running a tad lean continuously by not fully closing the EGR valve, but it's not lean enough to cause the code and then when the engine is put under extra load from the A/C compressor it pushes it over this threshold and causes the lean condition and the PCM stores the trouble code.
Be interested in seeing the results of giving the EGR valve a few light taps with a wooden or rubber mallet and disconnecting it.
Yeah that is pretty common. Sometimes it's actually a chunk of carbon stuck in the valve and by manually opening it the whole way when the engine is at 2,000 RPM can fix it. Most of the time, taking it off and cleaning the openings with some break cleaner and moving the valve back/forth manually and then putting it back on fixes it if the diaphragm is in good condition and assuming the DPFE module is functioning properly.
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OVERKILL
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Originally Posted by ram_man
Just did both of these things with no change .
OK. Have you looked for vacuum leaks? Intake tract sealing issues behind the MAF?
Just did both of these things with no change .
OK. Have you looked for vacuum leaks? Intake tract sealing issues behind the MAF?
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