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A. Penland
A. Penland, Ford Senior Master Technician, ASE
Category: Ford
Satisfied Customers: 6577
Experience:  ASE Master Certified, ASE Advanced Gasoline Engine Performance
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Codes P1131, P1151,P0136,P0156 idles rough. consistent to

Customer Question

Codes P1131, P1151,P0136,P0156 idles rough.
JA: Is the rough idle intermittent or consistent?
Customer: consistent to point of stalling occasionally while in gear at stop
JA: What is the model/year of your Ford?
Customer: 1998 F250
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: Checked the EGR system, all seems fine there, the EGR plunger moves
JA: Anything else you think the mechanic should know?
Customer: have full ODB scan too
Submitted: 11 months ago.
Category: Ford
Expert:  A. Penland replied 11 months ago.

These codes are caused either by a vacuum leak, low fuel pressure or a bad Mass Air Flow Sensor. Inspect the vacuum lines and the PCV hoses from the intake to the valve cover. Check the rubber elbows for cracks, stickiness and collapsed hoses. Then check the fuel pressure.

Customer: replied 11 months ago.
P0136 Freeze Data:
Fuel Sys 1 OL-Fault
Calc Load % 24.3
ECT 190
STFT B1 % 0
LTFT B1 % 0
STFT B2 % 17.1
LTFT B2 % 0
ENG RPM 1213
Veh Speed 31
Fuel Sys 1 OL Fault
Calc Load 36.0
ECT 194
STFT B1 3.1
STFT B2 2.3
Spark Adv 12
IAT 100
MAF lb/min 1.166
TPS % 18.4
O2S B1 S1 0
STFT B1 S1 3.1
O2S B1 S2 0.010
O2S B2 S1 0
STFT B2 S1 2.3
O2S B2 S2 0.010
More reading available at cold, running and parked hot.
Expert:  A. Penland replied 11 months ago.

Check for vacuum leaks on the PCV system first.

Customer: replied 11 months ago.
I did a 2500 rpm test for vacuum, pending purchase of a vaccum tester.
at idle, 800 rpm, Short Term Fuel Trim fluctuated 1.5 to 3.9
After 2 min, the Short Term Fuel Trim dropped to 0 on all banks and sensors.
returning to idle, 630 rpm, Short Term Fuel Trim fluctuated 1.5 to 2.3
Long Term Fuel Trim stayed at 0, probably from reseting the DTC.
Voltage on O2 Sensors stayed 0 to .025 varing from bank and sensorConfirm this looks like vaccum leak data, or O2 Sensor fouling, thanks.
Expert:  Chris (aka- Moose) replied 11 months ago.

Welcome, I'm Chris (aka Moose) I prefer to work when others don't, I am here around lunch and after dinner till after midnight.

The previous tech has opted out. Would you like me to help with this air fuel ratio issue?

This is my 1st answer, but does not have to be my only answer. You the website and myself expect you to have a great experience with my help. Please let me know if you are pleased by selecting a star rating above or by replying and saying your pleased. Not rating or rating 1-2 stars does not benefit you nor me in any way. Follow up and reply as often and when needed, there is no extra charge to do so.

Thanks Moose.

Expert:  Chris (aka- Moose) replied 11 months ago.

Hello again Chris here,

  • I am following up with you to see if you got everything you needed from my answer. We're you pleased with my help?
  • If you were not pleased with my help, please let me know by replying so I can help more.
  • This post is coming up on the 7 day mark where it times out. When a post times out, that means it's no longer on my active list (you reply and I may never know it.)

Thanks Chris

Customer: replied 11 months ago.
I am still trouble shooting for a vacuum leak, based on above results.
Sometimes after traveling at higher speed the idle will stick high, until it settles back down or not.
I have tried propane hosing to see if idle change
I still need to try carburetor washing of gaskets.
I have closed off the PVC line from TB and no change
There is no change with isolating the EGR valve either
There is good vacuum on the small actuator lines I can reach and remove.
Expert:  Chris (aka- Moose) replied 11 months ago.

At operating temp in park what is the short term fuel trim on both banks?

Customer: replied 11 months ago.
See if the attached excel makes sense for fuel trim readings
Expert:  Chris (aka- Moose) replied 11 months ago.

If there was a vacuum leak your short and long term trims would be pegged at the max +20. The spec is +/-10. Your average is not out of specs meaning this is not a vacuum leak to blame.

Customer: replied 11 months ago.
Would you recommend checking all the O2 sensor then?
Expert:  Chris (aka- Moose) replied 11 months ago.

The PCM uses the O2 sensor reading to determine how long to pulse the fuel injectors. That would change the fuel trim readings. Without the trim readings out of whack and no O2 codes I can not see a way to blame the O2 sensors.

Customer: replied 10 months ago.
if the codes at the beginning of the thread (P1131, P1151,P0136,P0156 ) are not O2 sensor problems, and the fuel trim does not indicate a vacuum leak....where should I look for the rough idle and high idle?
Expert:  Chris (aka- Moose) replied 10 months ago.

I did not even remember about the previous codes mentioned long ago from the time delay between responses. I can not keep up efficiently on the topic at hand when there are days between posts. I will opt out and see if another wants to help.

Expert:  A. Penland replied 10 months ago.

Try unplugging the MAF (Mass Air Flow) sensor and drive the vehicle. See if you get the same codes and same drivability problems. A bad MAF can cause all the same problems.

Customer: replied 10 months ago.
I unplugged the MAF and Temp sensors
After running the engine to normal op temp and driving for 5 min I did not get P1131, P1151,P0136,P0156
I did get the expected P0113, P0102
Drivability was the same or worse, idle was rough before now engine will die while at low idle.
the occasional sticking of high idle (1600-1700rpm) was much more frequent, until enough load caused idle to drop.
Previously when testing, when isolating the idle air control valve air loop (before TB to IACV) the engine would start but not run.
See attached Live Data info.
Thanks for the insight
Expert:  A. Penland replied 10 months ago.

Plug the MAF back in, clear the codes and loosen the exhaust pipes from the manifolds and run the vehicle. It will be noisy, but see if thing change. This will check for clogged exhaust/bad converters.

Customer: replied 10 months ago.
That may take a little while...will reply when done...thanks
Expert:  A. Penland replied 10 months ago.


Customer: replied 10 months ago.
The exhaust manifold nuts are rust welded on, and the easy to reach O2 Sensor is stuck so the sensor socket won't get it off...this may take a few days.
Expert:  A. Penland replied 10 months ago.