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Home >> GMC >> 1991 >> Value Van 7.4 N >> Repair and Diagnosis >> External Pages >> Different car >> Section 71 (Engine Controls - Basic Testing - 5.9L Diesel) >> Preliminary Inspection & Adjustments >> Low Speed Idle Adjustment

Low Speed Idle Adjustment

WARNING: This page is about a different car, the 1995 Dodge Pickup and 1995 Dodge Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: High speed idle is pre-adjusted and adjustment screw is sealed at factory and cannot be adjusted.

To adjust low speed idle, connect an optical tachometer (Snap-on MT139 or Cummins tool division MTE3377462) to read engine RPM. Bring engine to operating temperature. Locate low speed idle adjustment screw at rear of fuel injection pump. Loosen lock nut and adjust to specified idle speed. See LOW IDLE SPEED (RPM)  table. Tighten lock nut when low speed idle adjustment is complete, and recheck.

LOW IDLE SPEED (RPM)

Application M/T RPM A/T RPM
5.9L Diesel (1) 780 (2) 750-800
(1) With manual transmission in neutral and air conditioning on.
(2) With automatic transmission in drive and air conditioning on.