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Home >> Mazda >> 2018 >> MX-5 Miata Club, Automatic Trans >> Repair and Diagnosis >> Engine Performance >> System >> Symptom Troubleshooting - Engine Control >> No. 12 Lack/Loss Of Power-Acceleration/Cruise >> Notes
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No. 12 Lack/Loss Of Power-Acceleration/Cruise: Notes

12 LACK/LOSS OF POWER-ACCELERATION/CRUISE
DESCRIPTION
  • Performance is poor under load. (e.g., power down when climbing hills)
Possible cause
  • Engine overheating
  • Drive-by-wire control system operates with brake override system
  • PCM DTC is stored
  • Erratic signal to PCM
    • APP sensor or related circuit malfunction
    • CPP switch or related circuit malfunction (MT)
    • Neutral switch or related circuit malfunction (MT)
    • Communication error between TCM and PCM (AT)
    • ECT sensor No. 1 or related circuit malfunction
    • Fuel pressure sensor or related circuit malfunction
    • IAT sensor No. 1 (integrated in MAF sensor/IAT sensor No. 1) or related circuit malfunction
    • MAF sensor or related circuit malfunction
    • MAP sensor or related circuit malfunction
    • A/F sensor or related circuit malfunction
    • HO2S or related circuit malfunction
    • Improper air/fuel mixture ratio control operation
    • Intermittent open or short circuit MAF sensor, APP sensor, TP sensor
  • Improper operation of A/C system
  • Improper operation of drive-by-wire control system
  • Throttle body malfunction
  • Incorrect fuel injection timing
  • Fuel injector malfunction
  • Purge solenoid valve malfunction
  • Fuel leakage
  • Poor fuel quality
  • Air leakage or restriction in intake-air system
  • Vacuum leakage
  • Air cleaner restricted or dirty
  • Clutch slippage (MT)
  • Brake dragging
  • Tire air pressure malfunction
  • Erratic signal from CKP sensor
    • Loose installation
    • Damaged trigger wheel (crankshaft pulley)
    • Open or short circuit in related wiring harness
  • Erratic or no signal from CMP sensor
    • Loose installation
    • Damaged trigger wheel (intake camshaft)
    • Damaged trigger wheel (exhaust camshaft)
    • Open or short circuit in related wiring harness
  • Inadequate fuel pressure (high or low pressure side)
    • Fuel pressure sensor malfunction
    • High pressure fuel pump malfunction
    • Spill valve control solenoid valve control circuit malfunction (damage to driver in PCM caused by short circuit to ground system)
    • Spill valve control solenoid valve (built-into high pressure fuel pump) malfunction
    • Relief valve (built-into high pressure fuel pump) malfunction
    • Fuel line restricted or clogged
    • Fuel filter clogged (built-into fuel pump unit)
    • Fuel pump mechanical malfunction
  • Throttle valve restricted or clogged
  • Low engine compression
  • Improper intake valve timing
  • Improper exhaust valve timing
  • Improper operation of electric variable valve timing control system
    • Electric variable valve timing driver malfunction
    • Electric variable valve timing motor malfunction
    • Electric variable valve timing actuator malfunction
  • Improper operation of hydraulic variable valve timing control system
  • Spark plug malfunction
  • Ignition coil malfunction
  • Exhaust system and/or TWC restriction
  • PCV valve malfunction
  • Injector driver (built-into PCM) malfunction
  • AT internal malfunction (AT)
Possible cause
WARNING:
  • The following troubleshooting flow chart contains the fuel system diagnosis and repair procedures. Read the following warnings before performing the fuel system services:
    • Fuel vapor is hazardous. It can easily ignite, causing serious injury and damage. Always keep sparks and flames away from fuel.
    • Highly pressurized fuel may spray out if the fuel line is cut. Due to the following dangers occurring with a fuel spray, always complete the "Fuel Line Safety Procedure" to prevent the fuel from spraying. (See BEFORE SERVICE PRECAUTION ).
  • Fuel may cause irritation if it comes in contact with skin and eyes.
  • If fuel ignites and causes a fire, it may lead to serious injury or death, and damage to property and facilities.
  • Fuel is highly flammable and dangerous. Fuel line spills and leakage can cause serious injury or death, and damage to equipment. Always refer to the "Quick Release Connector Removal/Installation (fuel system)" before performing the fuel hose installation, and execute the "Fuel Leakage Inspection" after installation. (See QUICK RELEASE CONNECTOR REMOVAL/INSTALLATION ). (See AFTER SERVICE PRECAUTION ).
CAUTION:
  • Disconnecting/connecting the quick release connector without cleaning it may possibly cause damage to the fuel pipe and quick release connector. Always clean the quick release connector joint area before disconnecting/connecting, and make sure that it is free of foreign material.
CAUTION:
  • Verify the malfunction symptom according to not only the PID value but also the symptom troubleshooting.

Related PIDs

Item (definition) Unit/Condition Definition Condition/Specification (Reference)
APP1 % Accelerator pedal opening angle (absolute value) input from APP sensor No. 1
  • Accelerator pedal released: Approx. 15.29%
  • Accelerator pedal fully depressed: Approx. 90.98%
V APP sensor No. 1 voltage
  • Accelerator pedal released: Approx. 0.77 V
  • Accelerator pedal fully depressed: Approx. 4.55 V
APP2 % Accelerator pedal opening angle (absolute value) input from APP sensor No. 2
  • Accelerator pedal released: Approx. 7.84%
  • Accelerator pedal fully depressed: Approx. 45.49%
V APP sensor No. 2 voltage
  • Accelerator pedal released: Approx. 0.38 V
  • Accelerator pedal fully depressed: Approx. 2.27 V
CPP (MT) Off/On Clutch pedal position
  • Clutch pedal released: Off
  • Clutch pedal fully depressed: On
CPP/PNP (MT) Off/On Shift lever position
  • Neutral: On
  • Other than neutral: Off
ECT °C, °F Engine coolant temperature input fromECT sensor No. 1
  • Displays ECT
V ECT sensor No. 1 voltage Ignition switched ON (engine off)
  • ECT is 92 °C {198 °F}: Approx. 0.65 V Idle (after warm up)
  • ECT is 93 °C {199 °F}: Approx. 0.64 V Racing (Engine speed is 2, 000 RPM)
  • ECT is 92 °C {198 °F}: Approx. 0.66 V Racing (Engine speed is 4, 000 RPM)
  • ECT is 93 °C {199 °F}: Approx. 0.64 V
FUEL_PRES KPa {MPA.EN_US}, mBar {BAR.EN_US}, psi, in H20 Fuel pressure input from fuel pressure sensor
  • Displays fuel pressure
V Fuel pressure sensor voltage Ignition switched ON (engine off)
  • Fuel pressure is approx. 3.6 MPa {37 kgf/cm 2 , 522 psi}: Approx. 1.01 V (ECT is 92 °C {198 °F}) Idle (after warm up)
  • Fuel pressure is approx. 3.45 MPa {35.2 kgf/cm 2 , 500 psi}: Approx. 1 V (ECT is 92 °C {198 °F}) Racing (Engine speed is 2, 000 RPM)
  • Fuel pressure is approx. 3.21 MPa {32.7 kgf/cm 2 , 466 psi}: Approx. 0.96 V (ECT is 86 °C {187 °F}) Racing (Engine speed is 4, 000 RPM)
  • Fuel pressure is approx. 5.59 MPa {57.0 kgf/cm 2 , 811 psi}: Approx. 1.29 V (ECT is 84 °C {183 °F})
IAT °C, °F Intake air temperature (No. 1) input from IAT sensor No. 1
  • Displays IAT (No. 1)
V IAT sensor No. 1 voltage
  • IAT is 60 °C {140 °F}: Approx. 1.13 V
  • IAT is 63 °C {145 °F}: Approx. 1.07 V
  • IAT is 65 °C {149 °F}: Approx. 1.01 V
LOAD % Ratio of actual amount of intake air to the maximum air charging amount (mass volume) of cylinder
  • Idle (after warm up): Approx. 27.05% (ECT is 91 °C {196 °F})
  • Racing (engine speed is 2, 000 RPM): Approx. 16.86% (ECT is 89 °C {192 °F})
  • Racing (engine speed is 4, 000 RPM): Approx. 17.64% (ECT is 87 °C {189 °F})
LONGFT1 % Fuel learning correction amount estimated based on A/F sensor signal
  • Idle (after warm up): Approx. -1.56% (ECT is 91 °C {196 °F})
  • Racing (engine speed is 2, 000 RPM): 2.34% (ECT is 89 °C {192 °F})
  • Racing (engine speed is 4, 000 RPM): 2.34% (ECT is 87 °C {189 °F})
MAF g/Sec Mass air flow input from MAF sensor
  • Displays MAF
V MAF sensor voltage
  • Ignition switched ON (engine off) (MAF: 0.39 g/s {0.052 lb/min}): Approx. 0.72 V (ECT is 89 °C {192 °F})
  • Idle (after warm up) (MAF: 4.29 g/s {0.567 lb/min}): Approx. 1.15 V (ECT is 88 °C {190 °F})
  • Racing (engine speed is 2, 000 RPM) (MAF: 4.32 g/s {0.571 lb/min}): Approx. 1.15 V (ECT is 89 °C {192 °F})
  • Racing (engine speed is 4, 000 RPM) (MAF: 12.71 g/s {1.681 lb/min}): Approx. 1.66 V (ECT is 89 °C {192 °F})
MAP KPa {MPA.EN_US}, mBar {BAR.EN_US}, psi, in H20 Manifold absolute pressure input from MAP sensor
  • Displays MAP
MAP_V V MAP sensor voltage
  • Ignition switched ON (engine off) (MAP:101 kPa {1.03 kgf/cm 2 , 14.6 psi}): Approx. 4.08 V (ECT is 89 °C {192 °F})
  • Idle (after warm up) (MAP: 31 kPa {0.32 kgf/cm 2 , 4.5 psi}): Approx. 1.25 V (ECT is 88 °C {190 °F})
  • Racing (engine speed is 2, 000 RPM) (MAP: 32 kPa {0.33 kgf/cm 2 , 4.6 psi}): Approx. 1.31 V (ECT is 89 °C {192 °F})
  • Racing (engine speed is 4, 000 RPM) (MAP: 49 kPa {0.50 kgf/cm 2 , 7.1 psi}): Approx. 2.03 V (ECT is 89 °C {192 °F})
O2S11 μA A/F sensor current
  • Idle (after warm up): -59 μA (ECT is 92 °C {198 °F})
  • Deceleration fuel cut (accelerator pedal released from engine speed of 4, 000 RPM or more): Approx. 3.48 mA (ECT is 92 °C {198 °F})
O2S12 V HO2S voltage
  • Idle (after warm up): 0-1.0 V (ECT is 91 °C {196 °F})
  • Deceleration fuel cut (accelerator pedal released from engine speed of 4, 000 RPM or more): Approx. 0 V (ECT is 92 °C {198 °F})
RPM RPM Engine speed
  • Displays engine speed
SHRTFT1 % Fuel feedback correction amount estimated based on A/F sensor signal
  • Idle (after warm up): Approx. 0% (ECT is 91 °C {196 °F})
  • Racing (engine speed is 2, 000 RPM): Approx. 0.78% (ECT is 89 °C {192 °F})
  • Racing (engine speed is 4, 000 RPM): Approx. -21.87% (ECT is 87 °C {189 °F})
TP_REL % Throttle valve opening angle (relative value) with value at throttle valve fully close timing as the start point
  • Accelerator pedal released: Approx. 12.15%
  • Accelerator pedal fully depressed: Approx. 81.96%
VSS KPH, MPH Vehicle speed
  • Displays vehicle speed
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