1990 Chevrolet Forward Control 7.4 N, Automatic, 3L80-HD/M40FACTORY OEM SERVICE PROCEDURE

1990-91 Model Coverage & Identification

BODY, ENGINE, FUEL SYSTEM & IGNITION SYSTEM APPLICATIONS

Model Body Engine (1) VIN Fuel System Ignition
Astro & Safari M, L 4.3L (LB4) Z TBI Magnetic
4.3L (LU2)(2) B TBI Magnetic
Blazer & Jimmy V 5.7L (LO5) K TBI Magnetic
6.2L (LH6)(3) C Diesel N/A
6.2L (LL4)(4) J Diesel N/A
Lumina APV, Silhouette, Trans Sport U 3.1L (LG6) D TBI Magnetic
Parcel Van (P20/35) P 4.3L (LB4) Z TBI Magnetic
5.7L (LO5) K TBI Magnetic
6.2L (LH6)(3) J Diesel N/A
6.2L (LL4)(4) J Diesel N/A
7.4L (L19) N TBI Magnetic
Pickup (C/K 10/35), Sierra C, K 4.3L (LB4) Z TBI Magnetic
5.0L (LO3) H TBI Magnetic
5.7L (LO5) K TBI Magnetic
6.2L (LH6)(3) C Diesel N/A
6.2L (LL4)(4) J Diesel N/A
7.4L (L19) N TBI Magnetic
R/V 35 R, V 5.7L (LO5) K TBI Magnetic
6.2L (LH6)(3) J Diesel N/A
6.2L (LL4)(4) J Diesel N/A
7.4L (L19) N TBI Magnetic
Suburban, R/V 15/25 R, V 5.7L (LO5) K TBI Magnetic
6.2L (LH6)(3) J Diesel N/A
6.2L (LL4)(4) J Diesel N/A
7.4L (L19) N TBI Magnetic
S/T Series Blazer, Bravada, Jimmy, Pickup, Sonoma, Syclone S, T 2.5L (L38)(2) A TBI Magnetic
2.5L (LN8)(5) E TBI Magnetic
2.8L (LL2) R TBI Magnetic
4.3L (LB4) Z (6)TBI Magnetic
Van (G10/35), Rally Van, Vandura G 4.3L (LB4) Z TBI Magnetic
5.7L (LO5) K TBI Magnetic
6.2L (LH6)(3) C Diesel N/A
6.2L (LL4)(4) J Diesel N/A
7.4L (L19) N TBI Magnetic
]5.7L (L98) 8 PFI Magnetic
(1) Engine code is stamped on engine block. See ENGINE CODE LOCATION.
(2) High Output
(3) Light Duty emissions.
(4) Heavy Duty emissions.
(5) 2WD only.
(6) Port fuel injection on Syclone.
Factory Service Tools

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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.

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