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:
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.