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.
1986 Mercedes Benz 560SECFACTORY OEM SERVICE PROCEDURE
Lambda Control
- With engine at operating temperature, pull off purge line to throttle valve housing. Plug valve line. Connect on-off ratio tester to diagnostic socket. Press "100%" IR button.
- Test on-off ratio at 2500 RPM and read mean value. Compare this value with the idle speed value. The mean value at idle speed must be between 5-15% higher than the mean value measured at 2500 RPM. If not okay, go to step 3). If okay, test is complete.
- If reading is constant, test oxygen sensor or repair interruption as necessary. See OXYGEN SENSOR test in this section. If mean value is not 5 to 15% higher, adjust lambda control.
Factory Service Tools
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.
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.