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- #Fuel injector oscilloscope pattern how to
- #Fuel injector oscilloscope pattern code
- #Fuel injector oscilloscope pattern professional
Starting in the mid-’90s, Toyota introduced a second-generation air flow sensor that combines the functions of the air flow meter and air temperature sensor into one unit. If the reading is out of specifications or fails to change as the temperature increases, the sensor is bad and needs to be replaced. You can use an ohmmeter to check the sensor’s output.
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Codes that would indicate a fault in the air temperature sensor circuit include 8, 23 and 24. The air temperature sensor changes resistance, so if the signal goes flat or disappears, it too can upset the air/fuel mixture and cause driveability problems. Cold air is denser than warm air, and requires a slightly richer fuel mixture. A buildup of varnish or dirt may cause binding, so be sure to inspect the air filter if you find any dirt in the unit.Ī temperature sensor located in the intake plumbing is used to measure air temperature so the computer can calculate how much air is actually entering the engine. There should be no binding when the flap is pushed open, and spring pressure should return it to its closed position. The flap-type air flow meters should also be inspected by pushing the flap with your finger. If you have a good air flow signal but injector dwell fails to increase as air flow goes up, there’s a control problem in the computer. If you don’t see a nice linear change in the output voltage as the flap moves from idle to wide open throttle, it means the potentiometer is skipping and the air flow meter needs to be replaced.Īnother way to check the operation of the air flow meter as well as the entire feedback circuit through the computer is to use a scope to compare injector dwell (on time) to the air flow signal. To find this kind of fault, an oscilloscope can help you analyze the air flow meter’s output voltage as a waveform.
#Fuel injector oscilloscope pattern code
The TCCS (Toyota Computer Control System) should set a code 2, 31 or 32 if the air flow meter signal is missing or out of range, but it may not always detect an intermittent problem. The result can be poor cold driveability, hesitation or poor performance. Shorts or opens in the circuitry will also disrupt the voltage signal, depriving the engine computer of this vital bit of information. Over time, the potentiometer’s contacts inside the air flow meter can wear, causing erratic or inconsistent readings. So the meter’s output voltage drops as air flow increases. The greater the air flow, the higher the resistance created by the potentiometer. This changes the air flow meter’s output voltage in proportion to air flow. Connected to the flap is an arm that rubs across a resistor grid (potentiometer). A flap inside the meter rotates when incoming air pushes against it. On the older Toyota EFI systems, air flow is measured mechanically with a flap-style air flow meter. To regulate the air/fuel mixture, the engine computer needs to know how much air is being sucked into the engine.
#Fuel injector oscilloscope pattern how to
So if you’ve encountered a Toyota with fuel-related driveability problems, here are some pointers on how the system works and tips on how to diagnose and repair those applications. Even so, older high-mileage cars and trucks can develop problems that are common to all fuel injection systems: Pumps wear out regulators fail injectors become dirty or worn cold start injectors can leak and intake systems can become restricted due to accumulated carbon and fuel varnish. The system has evolved over the years, earning a reputation for being relatively trouble-free. Toyota’s multi-port fuel injection system, based on Bosch L-Jetronic technology, has been used since the early 1980s on its family of engines. Toyotas TOYOTA FUEL INJECTION SYSTEM SERVICE: DIAGNOSING FUEL-RELATED DRIVEABILITY PROBLEMSĮdited from an article by Larry Carley, ImportCar, November 2000
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#Fuel injector oscilloscope pattern professional
Whether you are a professional or a DIY mechanic, you’re sure to find the tips you need to insure a job well done. Use this comprehensive information library whenever you need helpful hints from car repair professionals.