1988 Mercedes Benz 560SLFACTORY OEM SERVICE PROCEDURE

Engine Running

  1. Run engine at idle (operating temperature). Check ignition timing. Specification is 7-11 degrees. If not, go to next step. If okay, go to step 4).
  2. Pull plug from throttle valve switch connector. Test resistance of throttle valve switch on connector. Between terminals No. one and 2, (idle speed position) about zero ohms. Between terminals No. 2 and 3, (full load position) about zero ohms. Between terminals No. 1-2 and 2-3, (partial load) infinity (4). If not, adjust or replace throttle valve switch. If okay, replace ignition control module.
  3. Run engine at 3200 RPM. Check ignition timing (vacuum line connected). Specification is 40-44 degrees ATDC at 3200 RPM. If not, go to next step. If okay, go to step 6).
  4. Check vacuum line from intake manifold to ignition control module for leaks. If no leaks are present check resistance of reference resistor (EZL). Pull sensor signal input plug on ignition control module and check resistance with ohmmeter between connector terminal No. 3 and ground. Go to next step.
  5. Specification is 750 ohms. If okay, replace ignition control module. If not okay, check wire for interruptions or replace connector. Go to next step.
  6. Pull vacuum line from ignition control module and run engine at 3200 RPM. Check ignition timing. Specification is 27-31 degrees at 3200 RPM. If okay, go to step 8). If not okay, go to next step.
  7. Unplug coolant temperature sensor. Test resistance from sensor terminal to ground. Test resistance at 2 different temperatures. If not within specifications, replace sensor. See Figure . If values are okay, go to next step.
  8. Run engine at 3200 RPM (vacuum line connected). Check dwell angle. Specification is 24-53 degrees. If not okay, replace ignition control module. If okay, test is complete.
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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.