I thought the same, no misfire codes. Only code still is the P1131, yeah only did it at idling....

 

Has anyone plugged a scanner into this truck to look at pending codes, fuel trims and working parameters?

 

Clogged cat converter . .you can usually tell when an engine has a skip in it i/e not running on a cyl. It will shake at idle and dah dah dah when you hit the throttle in park. These engines run like crap with one cyl out. Early engines won't throw a miss code either . Start cold run for 15 seconds shut off and feel the exhaust of each cyl to see if hot.

 

Did you check to see if maybe you have a clogged or bad injector? How about the EGR? Could it possible be clogged up? At 224K on it, I wouldn't be surprised at either of these things happening.

 

Before throwing any more parts at the truck, I'd try to back up and look at this from a simplified perspective. Most times the simplest answer is the correct one. That includes what were the last things done before the symptoms occurred.

The assumption was originally made that the rough running occurred after you changed the fuel filter, but then made the comment that you "cleaned" the MAF sensor. The MAF sensor regulates your fuel delivery based on airflow, temperature and barometric pressure. If the MAF is not working properly, you could very easily get a lean condition. How did you clean the MAF sensor? Did you use the MAF cleaner, or another chemical? Did you use compressed air to blow out the sensor? Did you accidentally physically touch the inside of the sensor?
If you answered yes to the last two, then I suspect you may have inadvertently damaged the MAF sensor. They are very sensitive to physical damage. If you know someone with a decent OBDII reader with live data capabilities or an Ultragauge, you could connect it and check the MAF readings live while the truck is running. There are published specifications on what the sensor readings should be at idle.

 

He's said that he changed the filter because it was running rough.

I'd still hedge my bets on the fuel pump or the cat. Check both thoroughly before replacing, as both are expensive. I'd test the fuel pressure again but this time put a load on it. Rev it up really high for a sustained period of time, see if it drops at all. I don't have the fuel pressure standards handy but I'm sure you can find them. Or just call ford and ask.

 

Trying to find a guy that has a descent scanner.....

 

Tried it. No hot cylinder

 

Inspecting the EGR will be todays job. Feeling a little burned out though

 

Used MAF cleaner, blew it out with air and I did not touch the inside at all.

 

Compressed air isn't good for the MAF unless you were gentle. Lots of older guys will hit one with 100PSI or more. Game over for most of them.

 

Sounds like you have a vacuum leak after the MAF sensor, a bad MAF or the O2 sensor is reading incorrectly. If your reading good pressure at the rail the pump and filter are ok. Lack of spark would give you a rich condition. A non functioning injector should cause a misfire. Does it have upstream O2 sensors?

 

Did not pull any misfire codes just the P1131, it does have an upstream O2 sensor.

 

P1131 FORD - Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 1

Possible causes
•Faulty Upstream Oxygen Sensor Bank 1
•Fuel pressure high or low
•MAF sensor dirty/defective
•Vacuum leak on engine
•Leaking fuel injector or fuel pressure regulator
•Faulty Powertrain Control Module (PCM)

Tech notes
The code means that the Powertrain Control Module (PCM) has detected a lean system, which means that there is either not enough fuel or and excessive amount of air in the system. Start by checking for vacuum leaks.

When is the code detected?
When an HO2S sensor indicates lean at the end of a test, the system is trying to correct for an over-lean condition. The code is set when the fuel control system no longer detects switching for a calibrated amount of time.

Possible symptoms
•Engine Light ON (or Service Engine Soon Warning Light)

P1131 Ford Description
The Heated Oxygen Sensor (HO2S) Monitor is an on-board strategy designed to monitor the HO2S sensors for a malfunction or deterioration that can affect emissions. Under specific conditions, the fuel control or upstream HO2S sensors are checked for proper output voltage and response rate (the time it takes to switch from lean to rich or rich to lean). Downstream HO2S sensors used for Catalyst Monitor are also monitored for proper output voltage. Input is required from the Engine Coolant Temperature (ECT) or Cylinder Head Temperature (CHT), Inlet Air Temperature (IAT), Mass Air Flow (MAF), Throttle Position (TP) and Crankshaft Position (CKP) sensors to activate the HO2S Monitor. The Fuel System Monitor and Misfire Detection Monitor must also have completed successfully before the HO2S Monitor is enabled.

• The HO2S sensor senses the oxygen content in the exhaust flow and outputs a voltage between zero and 1.0 volt. Lean of stoichiometric (air/fuel ratio of approximately 14.7:1 for gasoline engines), the HO2S will generate a voltage between zero and 0.45 volt. Rich of stoichiometric, the HO2S will generate a voltage between 0.45 and 1.0 volt.

• The HO2S Monitor evaluates both the upstream (Fuel Control) and downstream (Catalyst Monitor) HO2S for proper function.

• Once the HO2S Monitor is enabled, the upstream HO2S signal voltage amplitude and response frequency are checked. Excessive voltage is determined by comparing the HO2S signal voltage to a maximum calibratable threshold voltage.

• A fixed frequency closed loop fuel control routine is executed and the upstream HO2S voltage amplitude and output response frequency are observed. A sample of the upstream HO2S signal is evaluated to determine if the sensor is capable of switching or has a slow response rate.

• An HO2S heater circuit fault is determined by turning the heater on and off and looking for a corresponding change in the OSM and by

measuring the current going through the heater circuit.

• The MIL is activated after a fault is detected on two consecutive OBD II drive cycles.

https://www.engine-codes.com/p1131_ford.html