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Engine Controls - System & Component Tests - 2.2L: Overview Pontiac Sunfire I

Testing & Diagnostics ~2159 words

MODEL IDENTIFICATION

Vehicle model is identified by fourth character of Vehicle Identification Number (VIN). VIN is stamped on metal pad on top of left end of instrument panel, near windshield. See MODEL IDENTIFICATION table.

Body Code (1)Model
"J"(2) Cavalier & Sunfire
"N"Alero & Grand Am
(1) Vehicle body code is fourth character of VIN. (2) Cavalier is available with gasoline and Bi-Fuel - CNG/Gasoline engines.
(1)Vehicle body code is fourth character of VIN.
(2)Cavalier is available with gasoline and Bi-Fuel - CNG/Gasoline engines.

MODEL IDENTIFICATION

Description

Water contamination in the fuel system may cause driveability conditions such as hesitation, stalling, no start, or misfires in one or more cylinders. Water may collect near a single fuel injector at the lowest point in the fuel injection system and cause a misfire in that cylinder. If the fuel system is contaminated with water, inspect the fuel system components for rust or deterioration.

Alcohol concentrations of 10 percent or more in the fuel can be detrimental to fuel system components. Alcohol contamination may cause fuel system corrosion, deterioration of rubber components, and subsequent fuel filter restriction. Some types of alcohol are more detrimental to fuel system components than others. Ethanol is commonly used in gasoline, but in concentrations of no more than 10 percent. Some fuels, such as E85, contain a very high percentage of ethanol. Fuel with more than 10 percent ethanol may cause driveability conditions such as hesitation, lack of power, stalling, or no start.

Water contamination in the fuel system may cause driveability conditions such as hesitation, stalling, no start, or misfires in one or more cylinders. Water may collect near a single fuel injector at the lowest point in the fuel injection system and cause a misfire in that cylinder. If the fuel system is contaminated with water, inspect the fuel system components for rust or deterioration.

Alcohol concentrations of 10 percent or more in the fuel can be detrimental to fuel system components. Alcohol contamination may cause fuel system corrosion, deterioration of rubber components, and subsequent fuel filter restriction. Some types of alcohol are more detrimental to fuel system components than others. Ethanol is commonly used in gasoline, but in concentrations of no more than 10 percent. Some fuels, such as E85, contain a very high percentage of ethanol. Fuel with more than 10 percent ethanol may cause driveability conditions such as hesitation, lack of power, stalling, or no start.

The scan tool is first used to energize the fuel pump relay. The fuel injector tester is then used to pulse each injector for a precise amount of time, allowing a measured amount of fuel into the manifold. This causes a drop in system fuel pressure that can be recorded and used to compare each injector. For a typical test example (Схема №4)

Test Description

The number below refers to the step number in the diagnostic procedure.

  1. 3 - The engine coolant temperature must be below the operating temperature to avoid irregular fuel pressure readings due to hot soak fuel boiling.

System Description

The scan tool is first used to energize the fuel pump relay. The scan tool is then used to pulse each injector for a precise amount of time allowing a measured amount of fuel into the manifold. This causes a drop in system fuel pressure that can be recorded and used to compare each injector. (Схема №4)

The number below refers to the step number in the diagnostic procedure.

  1. 3 - The Engine Coolant Temperature (ECT) sensor parameter must be below the operating temperature to avoid irregular fuel pressure readings due to hot soak fuel boiling.

The Powertrain Control Module (PCM) enables the appropriate fuel injector pulse for each cylinder. Ignition voltage is supplied directly to the fuel injectors. The PCM controls each fuel injector by grounding the control circuit via a solid state device called a driver. A fuel injector coil winding resistance that is too high or too low will affect engine driveability. A fuel injector control circuit DTC may not set, but a misfire may be apparent. The fuel injector coil windings are affected by temperature. The resistance of the fuel injector coil windings will increase as the temperature of the fuel injector increases.

The fuel tank leak test is used to locate any fuel or fuel vapor escaping the fuel tank area. Fuel vapors escaping above the fuel level will be detected when the Evaporative (EVAP) emission diagnostics complete one test cycle. The Malfunction Indicator Light (MIL) will illuminate after the EVAP diagnostics complete two test cycles.

The numbers below refer to the step numbers in the diagnostic procedure.

  1. 1 - Perform this procedure to determine that no EVAP diagnostic DTC is present.
  2. 3 - This test is to locate fuel leakage in the fuel lines.
  3. 4 - This tests for fuel leaks below the fuel tank fuel level.
  4. 5 - This test is to locate fuel vapors escaping above the fuel level in the fuel tank.

The Fuel Injector Control Module (FICM) enables the appropriate CNG fuel injector on the intake stroke for each cylinder. A voltage is supplied to the CNG fuel injectors through a pair of fuel injector relays. The FICM controls each fuel injector by grounding the control circuit via a solid state device called a driver. A fuel injector coil winding resistance that is too high, or low, will affect engine driveability. A fuel injector control circuit DTC may not set, but a misfire may be apparent. The fuel injector coil windings are affected by temperature. The resistance of the fuel injector coil windings will increase as the temperature of the fuel injector increases.

The numbers below refer to the step numbers in the diagnostic procedure.

  1. 3 - This step tests each fuel injector resistance within a specific temperature range. If any of the fuel injectors display a resistance outside of the specified value, replace the fuel injector.
  2. 4 - This step determines if all of the fuel injectors are within 0.5 ohm of each other. If the highest resistance value is within 0.5 ohm of the lowest resistance value, then all of the fuel injector coil windings are okay.
  3. 5 - This step determines which fuel injector is faulty. After subtracting the highest and lowest resistance values from the average value, replace the fuel injector that has the greatest resistance difference from the average.

The Fuel Injector Tester (J 39021) energizes the CNG fuel injector for a precise amount of time allowing a measured amount of fuel into the manifold. This causes a drop in system fuel pressure that can be recorded and used to compare each fuel injector.

The numbers below refer to the step numbers in the diagnostic procedure.

  1. 3 - The fuel pressure should be within the specified range. See Fuel System Diagnosis if the fuel pressure is not within the specified range.
  2. 5 - If the pressure drop value for each fuel injector is within 2.0 psi (14 kPa) of the average pressure drop value, the fuel injectors are flowing properly. Calculate the pressure drop value for each fuel injector by subtracting the second pressure reading from the first pressure reading.

The scan tool first energizes the following components for a precise amount of time allowing a measured amount of fuel into the manifold

  1. High Pressure Lock-Off (HPL).
  2. Low Pressure Lock-Off (LPL).
  3. CNG fuel injectors.

This causes a drop in system fuel pressure that can be recorded and used to compare each fuel injector.

The numbers below refer to the step numbers in the diagnostic procedure.

  1. 3 - The fuel pressure should be within the specified range. See Fuel System Diagnosis if the fuel pressure is not within the specified range.
  2. 4 - The fuel pressure should reach a steady value. See Fuel System Diagnosis if the fuel pressure does not stabilize.
  3. 5 - If the pressure drop value for each fuel injector is within 2.0 psi (14 kPa) of the average pressure drop value, the fuel injectors are flowing properly. Calculate the pressure drop value for each fuel injector by subtracting the second pressure reading from the first pressure reading.

The engine idle speed is controlled by the Idle Air Control (IAC) valve. The IAC valve is on the throttle body. The IAC valve pintle moves in and out of an idle air passage bore to control air flow around the throttle plate. The IAC valve consists of a movable pintle, driven by a gear attached to an electric motor called a stepper motor. The stepper motor is capable of highly accurate rotation, or of movement, called steps. The stepper motor has 2 separate windings that are called coils. Each coil is supplied current by two circuits from the Powertrain Control Module (PCM). When the PCM changes polarity of a coil, the stepper motor moves one step. The PCM uses a predetermined number of counts to determine the IAC pintle position. Observe IAC counts using a scan tool. The IAC counts will increment up or down as the PCM attempts to change the IAC valve pintle position. An IAC Reset will occur when the ignition key is turned to OFF position. First, the PCM will seat the IAC pintle in the idle air passage bore. Second, the PCM will retract the pintle a predetermined number of counts to allow for efficient engine start-up. If the engine idle speed is out of range for a calibrated period of time, an idle speed Diagnostic Trouble Code (DTC) sets.

The numbers below refer to the step numbers in the diagnostic procedure.

  1. 5 - This test determines the ability of the PCM and IAC valve circuits to control the IAC valve.
  2. 7 - This test determines the ability of the PCM to provide the IAC valve circuits with a ground. On a normally operating system, the test light should not flash while the IAC counts are incrementing.

Each ignition coil supplies secondary voltage to a pair of spark plugs. This is called a waste spark ignition system. The Powertrain Control Module (PCM) supplies Ignition Control (IC) signals to the Ignition Control Module (ICM). The ICM fires the correct ignition coil at the correct time based on the IC signals. The ICM detects if cylinder No. 1 or cylinder No. 3 is on the compression stroke by sensing the secondary voltage and polarity of each side of the ignition coil. The ICM detects this voltage with sensing circuitry integrated into each ignition coil. The higher voltage is on the compressing cylinder. The ICM provides a synthesized cam signal to the PCM based on these inputs. This is called compression sense ignition. The PCM uses the cam signals to synchronize fuel injection.

This system consists of the following circuits

  1. Ignition 1 voltage.
  2. Ground.
  3. Camshaft Position (CMP) sensor signal.
  4. IC timing control 2/3.
  5. IC timing control 1/4.

The numbers below refer to the step numbers in the diagnostic procedure.

  1. 4 - This step tests for a short to voltage in the ignition circuit.
  2. 5 - This step tests for a short to voltage in the battery circuit.

Each ignition coil supplies secondary voltage to a pair of spark plugs. This is called a waste spark ignition system. The Powertrain Control Module (PCM) supplies Ignition Control (IC) signals to the Ignition Control Module (ICM). The ICM fires the correct ignition coil at the correct time based on the IC signals. The ICM detects if cylinder No. 1 or cylinder No. 3 is on the compression stroke by sensing the secondary voltage and polarity of each side of the ignition coil. The ICM detects this voltage with sensing circuitry integrated into each ignition coil. The higher voltage is on the compressing cylinder. The ICM provides a synthesized cam signal to the PCM based on these inputs. This is called compression sense ignition. The PCM uses the cam signals to synchronize fuel injection.

This system consists of the following circuits

  1. Ignition 1 voltage.
  2. Ground.
  3. Camshaft Position (CMP) sensor signal.
  4. IC timing control - 2/3.
  5. IC timing control - 1/4.

The numbers below refer to the step numbers in the diagnostic procedure.

  1. 4 - This step tests for a short to voltage in the ignition circuit.
  2. 5 - This step tests for a short to voltage in the battery circuit.

A crankcase ventilation system is used to consume crankcase vapors in the combustion process instead of venting them to atmosphere. Fresh air from the intake system is supplied to the crankcase, mixed with blow by gases and then passed through a calibrated orifice into the intake manifold.

Operation

The primary control is through the Positive Crankcase Ventilation (PCV) orifice which meters the flow at a rate depending on inlet vacuum. The PCV orifice is an integral part of the camshaft cover. If abnormal operating conditions occur, the system is designed to allow excessive amounts of blow by gases to back flow through the crankcase vent into the intake system to be consumed by normal combustion.

Results of Incorrect Operation

A plugged orifice may cause rough idle, stalling or slow idle speed, oil leaks or sludge in engine. A leaking orifice may cause rough idle, stalling or a high idle speed.

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