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Home >> Mercedes Benz >> 1986 >> 560SL >> Repair and Diagnosis >> Engine Performance >> System >> Cis-E System >> Component Testing >> Engine Idle Speed Stabilization
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Engine Idle Speed Stabilization

  1. With engine at idle speed and operating temperature, place selector lever in a driving position. On 420 engine, idle speed should be about 575 RPM. On 560 engine, idle speed should about 525 RPM. If not okay, go to step 2). If okay, test is complete.
  2. Check input signal to idle speed control unit (between terminal No. 12 and battery. With selector lever in "P" or "N", engage into a driving position ("D"). Voltage should drop. If not okay, repair wire interruption. If okay, test is complete.
  3. With engine at idle speed and operating temperature, turn A/C compressor on. Place selector lever in "P" or "N" position. On 420 and 560 engine, idle speed should be about 675 RPM. If not okay, go to step 4). If okay, test is complete.
  4. Connect test cable to idle speed air valve. Set multimeter to mA scale. Start engine and run at idle and operating temperature. Engage and disengage A/C compressor. When engaging A/C compressor the current at idle speed air valve jumps by about 60 mA. If not okay, repair interruption according to wiring diagram. If okay, test is complete.
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