2005 V6 Mustang. HELP rough idle - Ford Mustang Forum
 
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post #1 of 5 (permalink) Old 09-18-2014 Thread Starter
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2005 V6 Mustang. HELP rough idle

i have a 2005 mustang v6 has rough idle scan shows code
p0171
p0174
p0191
p0193
i put a bottle of stp fuel injector cleaner didnt help much, i have changed the fuel filter, when i go beyond 3500 rpm there is a sound of air escaping from the engine, the car has a rough idle starts fine runs fine for 30 min or so but then has problems accelerating and sometimes even dies but starts back up in a few min but still has rough idle
Thanks in advance

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post #2 of 5 (permalink) Old 09-18-2014
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Get some CRC Throttle Body Cleaner and CRC Mass Airflow Sensor Cleaner and clean both. Spray the throttle body and clean with a bottle brush. Spray the MAF and let it dry before you plug it back in. Check back to see how it did.


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post #3 of 5 (permalink) Old 09-18-2014
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P0171 [COLOR=blue !important][COLOR=blue ! important]System[/COLOR][/COLOR] Too Lean - Bank No. 1.
P0174 System Too Lean - Bank No. 2.
P0191 Engine Fuel Temperature Sensor circuit.
P0193 Engine Fuel Temperature Sensor circuit.

So with the sound you describe - check for a vacuum leak that is causing unmetered air to enter the system giving you the first two codes. Have you done any mods to the car that you haven't listed?

P0191
P0193
Some searching brought up a possibility for those codes related to fuel issues:

Possible causes
- Low or no fuel
- Faulty Rail Pressure (FRP) Sensor
- FRP harness is open or shorted
- FRP circuit poor electrical connection
- Faulty Fuel Pump

Read more: P0193 Ford Fuel Rail Pressure Sensor Circuit High Input OBDII Engine Light Trouble Code | Engine-Codes.com

Fuel Rail Pressure Sensor Circuit Range/Performance

Our emissions expert has put together the following information about the P0191 fault code. We have also included diagnostic procedures you can take to your repair shop if the mechanic is having difficulty analyzing the code.
OBD II Fault Code
  • OBD II P0191
Fault Code Definition
  • Fuel Rail Pressure Sensor Circuit Range/Performance
What does this mean?
The Power Train Control Module or PCM needs to know the fuel pressure at all times. This is so the PCM can effectively control the fuel injectors so they deliver the optimal amount of fuel into the engine's combustion chambers for maximum power and economy while maintaining the lowest tail pipe emissions.


Code P0191 indicates that the signal from the Fuel Rail Pressure Sensor and/or its circuit is sending erratic readings, indicating a fuel pressure condition that is abnormal.


Symptoms
  • Check Engine Light will illuminate
  • Fuel Consumption may be higher than normal
  • Tail pipe emissions may smell unusual
  • Engine hesitation or stalling
  • Engine may die/stall at stop signs
  • Rich Fuel trim codes (P0172 fuel system to rich) may be triggered
  • Lean Fuel trim codes (P0171 fuel system too lean) may be triggered
  • Vehicle fails emissions test
  • In rare cases, no abnormal symptoms may be noticed
Common Problems That Trigger the P0191 Code
  • Defective Fuel Pressure Sensor
  • Defective Fuel Pressure Sensor Circuit or connector
  • Damaged/Defective Fuel pressure regulator
Common Misdiagnoses
  • Fuel Rail Pressure Sensor is replaced when the cause is a defective Fuel Pressure Regulator
  • Fuel Rail pressure Sensor is replaced when the cause is a defective fuel pump
  • Fuel Rail Pressure Sensor is replaced when the cause is a poor connection or chafed wiring
P0191 Diagnostic Theory for Shops and Technicians
First thing to do is to gather the Freeze Frame Data in order to analyze the engine's operating conditions when the code was set. Then, test drive the vehicle with a quality data streaming scan tool and watch the fuel pressure PID. Do the fuel pressure readings seem normal? If not, test the actual fuel pressure with a mechanical fuel pressure gauge to see if the sensor and/or its circuit is at fault or, if there is a fuel pressure problem. If the fuel pressure is normal, then test the Fuel Rail Pressure Sensor connector and wiring with a labscope to verify the circuitry is intact. If the circuitry is intact, and the 'real' fuel pressure is normal, then the Sensor is most likely at fault.
If the fuel pressure is erratic i.e too high, then too low etc I would inspect the fuel delivery system in order to determine the cause of the erratic fuel pressure. I would also perform an amperage draw on the fuel pump to see how much current it is using.


P0193 code Fuel Rail Pressure Sensor Circuit High Input.
Possible causes
- Low or no fuel
- Faulty Rail Pressure (FRP) Sensor
- FRP harness is open or shorted
- FRP circuit poor electrical connection
- Faulty Fuel Pump
What does this mean?

Possible symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
- Engine will not start
P0193 Ford Description
The Fuel Rail Pressure (FRP) sensor is a diaphragm strain gauge device in which resistance changes with pressure. The electrical resistance of a strain gauge increases as pressure increases, and the resistance decreases as the pressure decreases. The varying resistance affects the voltage drop across the sensor terminals and provides electrical signal to the Powertrain Control Module (PCM) corresponding to pressure.
Strain gauge type sensors are consider passive sensors. A passive sensor is connected to a voltage divider network so that varying the resistance of the passive sensor causes a variation in total current flow.
Voltage that is dropped across a fixed resistor in series with the sensor resistor determines the voltage signal at the PCM. This voltage signal is equal to the reference voltage minus the voltage drop across the fixed resistor.
The FRP sensor measures the pressure of the fuel near the fuel injectors. This signal is used by the PCM to adjust the fuel injector pulse width and meter fuel to each combustion cylinder.


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post #4 of 5 (permalink) Old 09-20-2014 Thread Starter
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Got magnaflow cat back and thats about it other are just visual i did spray the throttle body didn't help much should i change the fuel pressure sensor?

Last edited by shujatk; 09-20-2014 at 06:36 PM. Reason: mistakes
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post #5 of 5 (permalink) Old 09-21-2014
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If you can hear air escaping the engine have someone else rev the car with the hood up and listen to the sound to try and pinpoint it.
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