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.
1985 BMW 735i AutomaticFACTORY OEM SERVICE PROCEDURE
MOTRONIC CEC System
- Description
- Operation
- Trouble Shooting
- MOTRONIC System
- Notes
- Cold Engine Will Not Start
- Cold Engine Starts, But Stalls
- Cold Engine Hard to Start
- Warm Engine Will Not Start
- Erratic Idle/Warm-Up Phase
- Engine Backfiring
- Idle Speed Incorrect
- Accelerator Hesitation
- Accelerator Knock
- Coasting Hesitation
- Engine Misfiring All Conditions
- High Fuel Consumption
- CO Level Incorrect
- HC and NOx Excessive
- MOTRONIC System
- Testing
- Preliminary Testing
- Test Equipment
- Test 1: Fuel Pressure
- Test 2: Fuel Injectors
- Test 3: MOTRONIC Control Unit
- Test 4: Cold Start Valve
- Test 5: Idle Control Valve
- Test 6: DME Control Unit
- Test 7: Idle Control Unit
- Test 8: Engine Speed Sensor & Reference Point Pickup
- Test 9: Air Flow Sensor
- Test 10: Throttle Position Sensor
- Test 11: Coolant Temperature Sensor
- Test 12: Coolant Temperature Switch
- Test 13: THERMO Timer
- Test 14: Air Temperature Sensor
- Test 15: Oxygen Sensor
- Wiring Diagrams
Factory Service Tools
Use the Manual With the Right Hardware
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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.
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