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Home >> GMC >> 1987 >> Magnavan 5.7 M, 400/M40 >> Repair and Diagnosis >> Engine Performance >> System >> Fuel Injection System - TBI >> Trouble Shooting >> Hesitation, Sag Or Stumble

Hesitation, Sag Or Stumble

  1. Perform all preliminary checks. Check fuel pressure. See FUEL SYSTEM PRESSURE TEST . Check fuel for water contamination. Check TPS for binding or sticking. Check ignition timing.
  2. Check alternator output voltage. Repair alternator if output voltage is less than 9 or more than 16 volts. Check for an open in HEI ground circuit and repair as required. Check canister purge system for proper operation.
  3. Check EGR valve operation. See appropriate EGR SYSTEM CHECK chart in GENERAL MOTORS COMPUTER COMMAND CONTROL article in COMPUTERIZED ENGINE CONTROLS section.
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