My '94 Mustang GT 5.0L 5 speed has no power. Well, maybe 100
horsepower. It shows flashes of normal horsepower, but only briefly,
after a hot soak in hot (100-degree-plus) weather. After a minute or
so, it returns to its "normal," which is an extreme lack of power and
unwillingness to rev over 3800 RPM.
Here is the deal: 160,000 miles on the original engine. Good
compression, clean looking (tan) plugs, no excessive oil consumption,
normal (mid teens) city gas mileage. Engine is dead stock. No
internal or bolt on mods. TPS voltage appears normal, as does fuel
pressure (39 psi).
Fuel filter, fuel pump and screen, High-flow catalytic H-pipe, O2
sensors, EGR valve, computer, plug wires, cap, rotor, 195-degree
Consistent "EGR lean" codes (171 and 176), no other codes.
Any body with some wisdom on this? We are baffled.