Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
1990 Lexus ES 250 AutomaticFACTORY OEM SERVICE PROCEDURE
Idle Mixture
NOTE:
Idle mixture must be checked with air cleaner installed, all air intake system hoses and vacuum lines connected, EFI system wiring connectors tight, transmission/transaxle in Neutral, all accessories and cooling fan off (if equipped) and engine at normal operating temperature.
- Ensure idle speed is within specification. Install jumper wire between proper terminals of check engine connector. Connect positive (+) probe of voltmeter to terminal "VF" or "VF1" and negative (-) probe to terminal "E1". See Figure.
- Start engine and maintain engine RPM at 2500 RPM for approximately 2 seconds. With engine RPM at 2500, count the amount of times that voltmeter fluctuates between the specified voltage. See IDLE MIXTURE TEST SPECIFICATIONS TABLE.
- If the amount of fluctuations is less than the minimum amount, check for air leaks at the air induction system, defective airflow meter or throttle body.
- If fluctuations were within specification, accelerate and hold engine at 2500 RPM for approximately 2 minutes. Install exhaust gas analyzer probe in tailpipe at least 1.3 feet. Wait one minute and check idle mixture readings. If readings are not within specification, see IDLE MIXTURE TROUBLE SHOOTING TABLE.
IDLE MIXTURE TEST SPECIFICATIONS
| Voltage | Minimum Fluctuations |
|---|---|
| 0-5 | 8 Per 10 Seconds |
Factory Service Tools
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- β’ You smell fuel, burning insulation, or see smoke.
- β’ Brakes feel soft, pull hard to one side, or make grinding noises.
- β’ The engine overheats, stalls repeatedly, or misfires under load.
- β’ You are missing required tools, torque specs, or safe lifting equipment.
- β’ You are not confident in the next step or safety outcome.
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