Vehicle

GMC Sonoma

The compact pickup, and mechanically a Chevrolet S-10 — same frame, same engines, same transmissions — so S-10 information is the right information throughout. The 4.3 Vortec V6 is the engine most carry, and the fault that defines it is the central port injection assembly, the spider with its poppet nozzles sitting under the upper intake: the nozzles leak and stick, producing rough running, hard starting and fuel-trim codes that look like an oxygen-sensor or fuelling fault and are not. It is a replacement item rather than a diagnosis — and it is worth confirming the generation first, because the pre-1994 trucks (sold as the S-15 until 1991) use throttle-body injection on the same 4.3 and have none of it. On four-wheel-drive trucks the vacuum-actuated front axle engagement is the other recurring complaint.

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GMC Sonoma, front view — Elise240SX · CC BY-SA 4.0 (external)

Generations

First generation 1982–1993

Launched as the S-15 and renamed Sonoma in 1991; throttle-body injection on the 4.3 rather than the later central port system.
Body styles

Pickup

Platform

GM GMT325
Engines
1.9 four-cylinder — LR1 · petrol · 61 kW (82 hp) · 137 Nm (101 lb-ft)

2.5 four-cylinder — L38 · petrol · 78 kW (105 hp) · 183 Nm (135 lb-ft) · Iron Duke

2.8 V6 — LR2 · petrol · 203 Nm (150 lb-ft)

4.3 V6 — L35 · petrol · 145 kW (195 hp) · 353 Nm (260 lb-ft) · throttle-body injection

2.2 diesel — LQ7 · diesel · 46 kW (62 hp) · 130 Nm (96 lb-ft) · Isuzu-sourced

1.95 — LR1 · petrol

2.0 — LQ2 · petrol · 146 Nm (108 lb-ft)
Transmissions

3-speed THM-200C automatic · 4-speed Isuzu S101 manual · 4-speed BorgWarner T4 manual · 4-speed 700R4 automatic · 4-speed 4L60 automatic · 4-speed 4L60-E automatic · 5-speed Getrag 290 manual · 5-speed 5LM60 manual · 5-speed NV3500 manual · 5-speed BorgWarner T5 manual

Drivetrain

Rear-wheel drive · Part-time four-wheel drive with low range
Second generation 1994–2004

The Chevrolet S-10's twin; the 4.3's central port injection spider is behind most rough-running and fuel-trim faults.
- New Venture NV3500 5-speed manual
- T-5 manual
Body styles

Pickup

Platform

GM GMT325
Engines
2.2 four-cylinder — LN2 · petrol · 176–190 Nm (130–140 lb-ft)

4.3 V6 — petrol · Vortec L35

4.3 V6 — LB4 · petrol · 116–123 kW (155–165 hp) · 319 Nm (235 lb-ft)
Transmissions

4-speed 4L60-E automatic · 5-speed BorgWarner T-5 manual · 5-speed NV1500 manual · 5-speed NV3500 manual

Drivetrain

Rear-wheel drive · Part-time four-wheel drive with low range

Information, not instruction

CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.

Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.

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