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.
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HOMESERVICE MANUALSPLYMOUTH1990COLT L4-1468CC 1.5L SOHCREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSADJUSTMENTS
1990 Plymouth Colt L4-1468cc 1.5L SOHC
Computers and Control Systems: Adjustments
1990 Plymouth Colt L4-1468cc 1.5L SOHCSECTION Adjustments
CURB IDLE SPEED INSPECTION
NOTE: Adjustment of the idle speed is usually unnecessary.
Idle speed on fuel injected vehicles is controlled by the MPI Control Unit through the Idle Speed Control System.
Before checking the CURB idle speed, be sure:
^ Engine coolant temperature has reached 85-95~C (185-205~F)
^ Engine cooling fan, lights* and electrical accessories are OFF
^ Transaxle is in NEUTRAL or PARK.
^ Steering wheel is at a center position (power steering equipped)
^ Parking brake is applied.
^ Verify that the ignition timing is set to specifications. Refer to SPECIFICATIONS/ELECTRICAL.
CAUTION: Improper setting of the throttle valve opening will increase exhaust gas temperatures at deceleration, which will greatly reduce the life of the Catalytic Converter. Also, fuel consumption and engine braking will be affected.
1. Connect a tachometer to the engine speed detection terminal.
2. Start and run the engine for more than 5 seconds at 2,000 to 3,000 rpm.
3. Reduce the rpm and let the engine idle for 2 minutes.
4. Read the CURB idle speed. Refer to SPECIFICATIONS/MECHANICAL.
NOTE: Adjustment of the idle speed is usually unnecessary.
Idle speed on fuel injected vehicles is controlled by the MPI Control Unit through the Idle Speed Control System.
Before checking the CURB idle speed, be sure:
^ Engine coolant temperature has reached 85-95~C (185-205~F)
^ Engine cooling fan, lights* and electrical accessories are OFF
^ Transaxle is in NEUTRAL or PARK.
^ Steering wheel is at a center position (power steering equipped)
^ Parking brake is applied.
^ Verify that the ignition timing is set to specifications. Refer to SPECIFICATIONS/ELECTRICAL.
Tachometer Connection:
CAUTION: Improper setting of the throttle valve opening will increase exhaust gas temperatures at deceleration, which will greatly reduce the life of the Catalytic Converter. Also, fuel consumption and engine braking will be affected.
1. Connect a tachometer to the engine speed detection terminal.
2. Start and run the engine for more than 5 seconds at 2,000 to 3,000 rpm.
3. Reduce the rpm and let the engine idle for 2 minutes.
4. Read the CURB idle speed. Refer to SPECIFICATIONS/MECHANICAL.
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.