Iron Duke

Iron Duke is a common nickname for the 2.5L four-cylinder engine used in the Pontiac Fiero.

The Fiero's four-cylinder engine was part of Pontiac's 2.5L engine family. It was used in all 1984 Fieros and remained available through the 1988 model year. Later versions were also commonly referred to as the Tech IV or Tech 4.

Overview

The Iron Duke was the base engine in the Pontiac Fiero.

It was designed as an economical and durable four-cylinder engine rather than a high-performance engine. In the Fiero, it provided good fuel economy and simple maintenance, while the 2.8L V6 became the performance engine option beginning in 1985.

Location

Image wanted: Photo or diagram showing the 2.5L Iron Duke / Tech 4 engine installed in a Pontiac Fiero engine bay.

The Iron Duke is mounted transversely behind the passenger compartment in the Fiero engine bay.

Fiero applications

The 2.5L four-cylinder engine was used in:

• 1984 Pontiac Fiero
• 1985 Pontiac Fiero
• 1986 Pontiac Fiero
• 1987 Pontiac Fiero
• 1988 Pontiac Fiero

Year-to-year changes

The Iron Duke / Tech 4 changed during Fiero production. Some changes were mechanical, while others involved engine management, emissions equipment, accessories, or related systems.

1984

The 1984 Fiero used the 2.5L four-cylinder engine as its only available engine.

Notable points:

• 2.5L four-cylinder engine
• Crossflow cylinder-head design
• Throttle-body fuel injection
• Distributor ignition

1985

The 1985 model year continued use of the 2.5L four-cylinder engine.

Reported or commonly noted changes include:

• Roller cam introduced during the model year
• Engine later formally referred to as Tech 4 / Tech IV

Image wanted: Photo or reference image showing identifying differences between early and later Fiero 2.5L engines.

1986

The 1986 model year continued the 2.5L four-cylinder engine.

Reported or commonly noted changes include:

• Air-conditioning compressor changes on equipped cars

1987

The 1987 model year brought significant changes to the four-cylinder engine and engine-management system.

Reported or commonly noted changes include:

• Distributorless ignition system
• Updated ECM
• Intake air temperature sensor
• Updated throttle-body injection unit; Rochester-related TBI components are commonly listed for the 1987-1988 2.5L Fiero
• Elimination of ThermAC equipment

1988

The 1988 model year was the final year of Fiero production and used the later version of the four-cylinder engine.

Reported or commonly noted changes include:

• Balance shaft engine
• Integrated oil filter arrangement

Common topics

Common Iron Duke / Tech 4 topics include:

• Throttle body
• Fuel system
• Ignition system
• Cooling system
• Diagnostic trouble codes
• Oil filter
• Engine swaps

Notes

Some year-to-year details may vary by production date, emissions configuration, transmission, or equipment.

Because the 2.5L engine changed during Fiero production, parts should be verified by year, VIN, engine configuration, and actual installed components before ordering replacements.

See also

• Engine
• 2.5L four-cylinder
• 1984 Pontiac Fiero
• 1985 Pontiac Fiero
• 1986 Pontiac Fiero
• 1987 Pontiac Fiero
• 1988 Pontiac Fiero
• Factory specifications
• Parts interchange