Questions and Answers

Chevy Caprice Has No Power Q. 1992 Chevy Caprice 305. I have a frustrating problem which started as intermittent a few weeks ago and is now constant. The motor starts just fine, but when put into any gear has hardly any power to move the car. The following has been done without any success;

• Had spark plugs changed
• Changed distributor cap and Rotor
• Cleaned and resistance tested spark plug wires
• Replaced fuel filter
• Tested operation of MAP sensor per Haynes manual
• Tested throttle position sensor
• Checked operation of PVC
• Removed throttle body and cleared blocked vacuum passages (PVC vacuum port completely plugged with carbon)
• Replaced throttle body base gasket
• Cleaned IAC valve with carburetor cleaner
• Confirmed EGR valve will stall engine when diaphragm moved
• No computer codes are indicated using service engine light flashes.
• Fuel Pump replaced last summer

Vacuum at MAP sensor reads 18" at start-up, engine runs smooth, after approx. 10 seconds something adjusts and vacuum drops to 9" to 12". The needle is fairly steady. Engine starts to run rough. This roughness seemed to co-relate when the loss of power occurs. Your suggestions would be greatly appreciated.

Regards,
Mike

A. Clogged catalytic convertor? Very possible. Also check the positive cable on the pass side under the hood auxiliary fuse block if equipped. They used to come loose and melt the stud interrupting important power supplies to main engine feeds.