Inspection Procedure

HINT:

• If is case that DTC besides misfire is memorized simultaneously, first perform the troubleshooting for them.
• Read freeze frame data using OBD II scan tool or hand-held tester. Because freeze frame data records the engine conditions when the malfunction is detected. When troubleshooting, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.
• When the vehicle is brought to the workshop and the misfire is not occurred, misfire can be confirmed by reproducing the condition or freeze frame data. Also, after finishing the repair, confirm that there is no misfire. (See the CONFIRMATION DRIVING PATTERN )
• On 6 and 8 cylinder engines, misfiring cylinder identification is disabled at high engine speed and only an general misfire fault code P0300 is stored instead of a cylinder specific misfire fault code (i. e., P0301 - P0308). Under the following conditions, only P0300 code may be stored.

  Misfire starts in the high engine speed area

  or

  Misfire occurs only in the high engine speed area

  Therefore, when a general misfire fault code (i.e., P0300) is only stored, start the engine and drive the confirmation pattern (See the CONFIRMATION DRIVING PATTERN ) and read the value of the misfire ratio for each cylinder. Perform the repair correspond to the high misfire ratio cylinder. After completing the repair, confirm no misfire is occurring by driving the confirmation pattern.

• When either of SHORT FT #1, LONG FT #1, SHORT FT #2 or LONG FT #2 in the freeze frame data is besides the range of +/-20 %, there is a possibility that the air-fuel ratio is inclining either to "rich" (-20 % or less) or "lean" (+20 % or more).
• When COOLANT TEMP. in the freeze frame data is less than 80°C (176°F), there is a possibility or misfire only during warming up.
• In the case that misfire cannot be reproduced, the reason may be because of the driving with lack or fuel, the use of improper fuel, a stain of ignition plug, and etc.

1. Check wire harness, connector and vacuum hose in engine room. 

   CHECK: 

   1. Check the connection conditions of wire harness and connector.
   2. Check the disconnection, piping and break of vacuum hose.
   1. NG: Repair or replace, then confirm that there is no misfire (See the  CONFIRMATION DRIVING PATTERN  ). 
   2. OK: Go to next step. 
2. Check connection of PCV hose. 
   1. NG: Repair or replace PCV hose. 
   2. OK: Go to next step. 
3. Check spark plug and spark of misfiring cylinder. 

   PREPARATION: 

   1. Remove the ignition coil (See REPLACEMENT ).
   2. Remove the spark plug.

   CHECK: 

   1. Check spark plug type.
   2. Check the electrode for carbon deposits.
   3. Check electrode gap.

   OK: 

   1. Iridium-tipped spark plug 

      Recommended spark plug: 

      DENSO made: SK20R11 

      NGK made: IFR6A11 

   2. No large carbon deposit present. 

      Not wet with gasoline or oil. 

   3. Electrode gap: 1.0 - 1.3 mm (0.039 - 0.051 in.) 

   PREPARATION: 

   1. Install the spark plug to the ignition coil, and connect the ignition coil connector.
   2. Disconnect the injector connector.
      Fig 1: Identifying Spark Plug & Ignition Coil

      Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   3. Be sure to ground the screw of the spark plug securely.

   CHECK: 

   Check if spark occurs while engine is being cranked.

   NOTE:

   • Do not crash the electrode gap.
   • To prevent excess fuel from being injected from the injectors during this test, don't crank the engine for more than 5 - 10 sec. at a time.

   OK: 

   Spark jumps across electrode gap. 

   1. NG: Replace or check ignition system (See  IGNITION  ). 
   2. OK: Go to next step. 
4. Check voltage of ECM terminal for injector of failed cylinder. 

   PREPARATION: 

   1. Remove the glove compartment (See ENGINE CONTROL MODULE (ECM) ).
   2. Turn the ignition switch ON.

   CHECK: 

   Measure the voltage between applicable terminal of the ECM connector and body ground.

   OK: 

   Voltage: 9 - 14 V 

   Fig 2: Checking Voltage Of ECM Terminal For Injector Of Failed Cylinder

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   Reference: INSPECTION USING OSCILLOSCOPE 

   With the engine idling, check the waveform between terminals #10 - #60 and E01 of the ECM connector.

   HINT:

   The correct waveform is as shown.

   Fig 3: Inspecting Oscilloscope Waveform

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   1. OK: Go to Step   6 . 
   2. NG: Go to next step. 
5. Check resistance of injector of misfiring cylinder (See  INJECTOR  ). 
   1. NG: Replace injector. 
   2. OK: Go to next step. 

      Check for open and short in harness and connector between injector and ECM (See  PROCEDURE  ). 

6. Check fuel pressure (See  FUEL PUMP  ). 
   1. NG: Check and repair fuel pump, fuel pipe line and filter (See  PRECAUTION  ). 
   2. OK: Go to next step. 
7. Check injector injection (See  INSPECTION  ). 
   1. NG: Replace injector. 
   2. OK: Go to next step. 
8. Check mass air flow meter (See  MASS AIR FLOW (MAF) METER  , Inspection). 
   1. NG: Replace mass air flow meter. 
   2. OK: Go to next step. 
9. Check engine coolant temperature sensor (See x ENGINE COOLANT TEMPERATURE (ECT) SENSOR  ). 
   1. NG: Replace engine coolant temperature sensor. 
   2. OK: Check compression pressure (See  INSPECTION  ), valve clearance (See  INSPECTION  ) and valve timing (See  INSTALLATION  ).