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Repair1014U, Repair Shop Ower
Category: Ford
Satisfied Customers: 709
Experience:  Diagnosticas & Electrical
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2000 Mustang GT 4.6 SOHC 5speed. Car sometimes works fine

Customer Question

2000 Mustang GT 4.6 SOHC 5speed. Car sometimes works fine and the next time i start it sounds and performs out of tune. When it is in this state I cannot use the A/C because the engine starts surging, stalls ocassionally and the check engine lights up. Next time I start it it's fine again. I replaced the TPS, spark plugs several times, cleaned the injectors, recently ordered the oxigen sensors. car has 130,000 miles.
Submitted: 4 years ago.
Category: Ford
Expert:  Repair1014U replied 4 years ago.

welcome to Just Answer.

It could be a vacuum leak like the intake gasket which is a common problem with this vehicle. Do you know what the codes are in the computer are or if there is no codes here is the possibility and test procedures for you.

Please let me know if you need more help.

Thank you

It is necessary to perform the Quick Test before continuing with this procedure. Failure to do so may result in incorrect diagnosis.

Step 3: No DTC(s) Present Symptom Charts
QT: Step 1: PCM Quick Test


    Note: If the vehicle was brought in with an emission compliance failure symptom, GO directly to Section 5; GO to EM1.

  • Complete preliminary checks looking for obvious concerns that may relate to the symptom. Check items such as those listed:
    • Related electrical connectors or fuses
    • Vacuum lines (leaks, routing)
    • Air intake system (leaks, restrictions)
    • Fuel quality (octane, contamination, winter/summer blend)
    • Cooling system (engine operating at proper temperature)
  • Access any related OASIS or TSB information (if available).
  • Complete PCM Quick Test to access any DTCs. Note any Key On Engine Off, Key On Engine Running (if engine runs) and Continuous Memory (MIL and non-MIL) DTCs.

    Note: If unable to access DTCs, or any scan tool communication concern exists, GO to QA1 in Section 5. For additional information on retrieving MIL and non-MIL DTCs, refer to Section 2, Diagnostic Methods (Continuous Memory Self-Test).

Were any DTCs present?
Yes No
If engine runs rough at idle and Key On Engine Running or Continuous Memory DTC(s) are present:

GO to Quick Test QT2 to check injector fault PIDS.

All Others:

GO to Section 4 (Powertrain DTC Charts) for direction to service DTC(s) after noting the following:

Service DTCs in the following order (for each mode, begin diagnosis with the first DTC output).
  1. Any KOEO DTC(s)
  2. Any KOER DTC(s)
  3. Any Continuous Memory DTC(s) (retrieve any available Freeze Frame Data)(disregard any identical/related Continuous DTC(s) of DTC(s) already serviced).
GO to Step 2: NO DTC(s) PRESENT SYMPTOM CHART INDEX for direction to proper STEP 3 Chart.

Note: If symptom is not listed, REFER to applicable Workshop Manual or GO to Z1 in Section 5 (for intermittent PCM system diagnostics).


    Note: An injector circuit fault could result in unrelated DTC(s) being received from the PCM.

  • Key on, engine off.
  • Access the INJxF PIDs (the "x" indicates the injector number). There will be one INJxF PID for each engine cylinder.
Do any of the INJxF PIDs indicate "Yes"?
Yes No
An injector circuit fault exists. KEY OFF. Disregard DTC(s).

For Natural Gas applications:

GO to HA60.

All Others:

GO to H56.
No fault detected by injector fault PIDs. KEY OFF. GO to Quick Test QT1 and follow the YES Action To Take for all others.

Chart 1

  • Starting Concerns: Stalls After Start
  • Stalls/Quits
  • Runs Rough
  • Misses
  • Buck/Jerk
  • Hesitation/Stumble
  • Surge
  • Unique Idle concerns: Rolling Idle

Note: For stalls on passenger car applications, engine may stall if left running while refueling. Advise customer to turn engine off while refueling to avoid contamination or damage to the EVAP system.

SYSTEM/COMPONENT REFERENCE (Section 5 Pinpoint Test unless noted)
  • Check The Following PIDs:
    • DPFEGR (if equipped) (hot idle value within 0.15V of KOEO value)
    • LONGFT1 / LONGFT2 (value between -20 and +20)
    • VPWR (value between 10.5 and 17.0 volts, and within 0.5 volts of battery voltage)
  • DPFEGR PID value not within 0.15V of KOEO value:
  • GO to HE100
  • LONGFT1 / LONGFT2 value low (-):
  • Continue diagnosis.
  • Concentrate checks in areas that would cause the engine to run rich.
  • LONGFT1 / LONGFT2 value high (+):
  • Continue diagnosis.
  • Concentrate checks in areas that would cause the engine to run lean.
  • VPWR not between 10.5 and 17.0 volts:
  • Go to the Charging System - General Information Section 414-00 of the Workshop Manual.
  • VPWR between 10.5 and 17.0 volts, but not within 0.5 of battery voltage:
  • CHECK B(+) supply to power relay (or CCRM). CHECK VPWR circuit between PCM and power relay or CCRM. CHECK PWR GND circuits.
  • For vehicles that run rough at idle:
  • With the key on, engine off, check the INJxF PIDs (the "x" indicates the injector number, there will be one INJxF PID for each engine cylinder). All INJxF PIDs must indicate "NO"?
  • INJxF PID(s) indicate "yes" (an injector circuit fault is indicated):
    • Natural Gas applications:
    • GO to HA60
    • All others:
    • GO to H56
  • For engine now starts but stalls in PARK or NEUTRAL:
  • If engine will start and run normally at part throttle, check Idle Air Control (IAC) System.
  • Engine will start and run normally, instead of stalling, at part throttle:
  • GO to KE2
  • Mass Air Flow (MAF) Sensor
  • Secondary Ignition System
  • Fuel Delivery System
  • For Natural Gas Applications:
  • GO to HB1
  • All Others:
  • GO to HC1
  • Exhaust System
  • PCV System
  • Natural Gas applications with rough idle:
  • Injector circuits between NG module and injectors.
  • EVAP System
  • Check for EVAP system blockages (engine stalls) or leaks (other symptoms). REFER to Evaporative Emissions, Section 303-13 in the Workshop Manual.
  • Automatic Transmission
  • Automatic Transaxle/Transmission - Section 307-01 of the Workshop Manual
  • Base Engine
  • Engine System - General Information, Section 303-00 of the Workshop Manual
  • Intake Air System
  • Continental, LS6/LS8, Windstar:
  • A/C pressure sensor input to PCM
  • Additional Testing
  • Additional Checks:

    NOTE: Some applications have a PID that will indicate whether the PCM is reducing torque (095E b0), and if so, why the torque is being reduced (095Eb1-13).

    • Correct PCM vehicle identification (VID) block information (refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM)
    • Be aware of engine RPM/speed limiting functions of the PCM (look for incorrect high vehicle speed signal from PSOM or VSS)
    • Drivelines
    • Manual transmission/clutch
    • Charging System
    • Traction control system (if equipped)
    • A/C system (for surge with A/C on)
    • Speed control system (for surge with speed control on)
    • A/C compressor diode, if equipped (for rolling idle)
  • Applicable section in Workshop Manual.

Thank you and please let me know if you need more help.
Customer: replied 4 years ago.
what kind of scanner do you recommend for this application?. I had a $50 scanner that was not much help and then i misplaced it or loaned it , I don't know, but would like to invest my money in the correct scanner. Also, I am no technician so the acronyms need to be deciphered (ie, INJxF PIDs )
Expert:  Repair1014U replied 4 years ago.
The best scanner is to use the diagnostic scanner like the snap on one. A code reader scanner will not work for the testing procedures.

But for now you check the PVC and get a vacuum pump gauge to check the if the problem you are having is a Vacuum leak.

If you lost your code reader, you can go to Autozone to rent the code reader for free. You just need to give a deposit to use it then when you return the tool you get all of your deposit back. Right the codes down and come back and let me know what they are so I can help you out more. Make sure you erase the codes while you have the scanner.

Thank you for getting back to me.