1977 Seville 5.7 with EFI looses power under a load
Seeking advice on my 1977 Cadillac Seville... Motor is a stock 5.7 Cadillac 350 with Electronic Fuel Injection. Fuel pressure varies between 38-43 psi, and will hold pressure for 30 seconds after the motor is shut off. The engine starts hard and runs excessively rich when cold (regardless of the season). Under modest acceleration the engine loads up and stalls without warning until driven for 15 minutes or so. After stalling, cranking the engine at wide open throttle starts it up running very rich. When reving the engine, it will not accelerate above 3000 RPM. When holding rpm where the engine begins to stumble, it will clear in about 15 seconds and smoothly revs to higher RPMs. At that point, the motor has enough power to gently pull into traffic on local roadways. Loading up and stalling repeats intermittently until the car has driven for 15 minutes or longer. After that the motor runs smoothly, albeit dramatically under-powered. This car accelerates from 0 to 60 in roughly 20 seconds and can barely climb hills or travel at highway speeds until after it fully warms up. I am torn between a defective fast idle valve heater or malfunctioning injectors. Anyone care to share their advice on how to resolve these issues? Thanks in advance!
Re: 1977 Seville 5.7 with EFI looses power under a load
First thought, defective coolant temp sensor. This car has that sensor plus an intake air temp sensor. Same part number. Swap one for the other. Coolant sensor is next to the thermostat housing, the air sensor is at the back of the intake manifold screwed into an intake runner. If that seems to fix it, then get a new sensor. The fast idle valve (choke heater) has no effect on fuel mixture, it simply allows the engine to have a faster idle when cold.