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Home >> Chevrolet >> 1986 >> Forward Control 7.4 W, Automatic, 400/M40 >> Repair and Diagnosis >> Engine Performance >> Ignition System >> Ignition System - HEI (Federal) >> Electronic Testing >> Poor Engine Performance

Poor Engine Performance

  1. Disconnect the 4-pin controller at the distributor and jumper pins A and C together at distributor connector. Test drive vehicle. If trouble remains, check for other possible causes. Refer to the TROUBLE SHOOTING - BASIC PROCEDURES article. If trouble is gone, proceed to step 2).
  2. Turn engine off, remove jumper and reconnect 4-pin connector. Disconnect 10-pin connector from controller. Make sure terminals are seated in connector and connection to controller is good. Check connector pins B and K for open or short circuits. Repair circuits as necessary.
  3. With multimeter J-29125-A set on DC in 2000 range, check resistance from pin B to pin K. Should read approximately 98-99 ohms. If initial reading is correct, go to step 4). If reading is not correct, disconnect sensor wire from sensor. Check resistance from terminal on sensor to ground. Should read approximately 98-99 ohms. If reading is correct, repair circuit from sensor to pin B. If reading is not correct replace sensor.
  4. Reconnect connector to controller. Measure voltage from connector pin F wire to connector pin K wire with engine control switch on.
  5. If reading is over 11.6 volts, measure voltage from pin H wire to pin K wire with engine control switch on and voltmeter on the AC, 20 range. Should be more than 0.2 volts. If reading is under 11.6 volts, repair circuit between engine control switch and pin F.
  6. If step 5) voltage is over 0.2 volts, test drive vehicle. If trouble remains, replace ESC controller. If voltage was less than 0.2 volts, repair harness.
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