The Associated Press quoted the National Highway Traffic Safety Administration as saying it had "...received 148 complaints regarding Pontiac Fieros catching fire including reports of six injuries.... Low levels of engine oil may cause a connecting rod to break, allowing oil to escape and come into contact with engine parts. The oil would catch fire when it contacted the exhaust manifold or hot exhaust components.... David Hudgens, a GM spokesman in Detroit... said, 'If you ran out of oil, and then that coupled with some aggressive driving, perhaps, and maybe not changing the oil very often, you end up with a broken rod, and that's where the connecting rod came in; it is still the owner's responsibility to check the oil.' "[5]
The Pontiac division claimed in a 1988 press release that "GM tests have shown that running these 1984 cars with low engine oil level can cause connecting rod failure which may lead to an engine compartment fire.... Pontiac is aware of 260 fires attributable to the condition, along with ten reported minor injuries."[6]
The larger of the two reported numbers of cars with fires (260) amounts to 0.07% of Fieros produced. The fires affected the 2.5 L engine almost exclusively, and mostly 1984 models (although there may have been additional occurrences after the above reports were published).
There are several possible contributors to Fiero engines catching fire. The primary cause is thought to be a batch of poorly cast connecting rods, produced in GM's Saginaw plant, which failed when the oil level became too low. One theory is that the sports car styling attracted buyers who would drive the car hard, most notably by over-revving the engine. Another factor was the incorrectly listed three-quart oil capacity; the actual oil capacity was 4.5 quarts, but a misprint on dipsticks and in the owner's manuals led to owners using only three quarts, perhaps resulting in a leaky valve cover gasket[clarification needed] which would allow the oil level to decline over time to a dangerously low level. If the proper oil level was not maintained, the bearings could seize, snapping the porous castings of the connecting rods. This could result in a hole being punched in the engine block, allowing oil to spray onto hot exhaust components where it could ignite.
Alternatively, some fires may have been due to the engine wiring harness being located in the center of the engine bay above the exhaust manifold, where the heat could possibly melt and ignite the wiring. The 1984 model had a magnesium grille over this area. In later models, this was improved to some degree with better heat shielding wrapped around the wiring harness.
A third cause might be cracks in the engine block from overtightenening of the head bolts. Some engines developed cracks in the block that would leak coolant and/or oil, sometimes accompanied by broken head bolts directly above the crack. The leak would spray coolant or oil, the latter resulting in fire if sprayed onto the hot catalytic converter or exhaust manifold at the front of the engine compartment.
