Cadillac Repair: lose of power, fuel pressure gage, perameters

Question
I have a SLS 1994 - it tends to lose power and run very bad when it reaches 40 mph or when air condition is on.

Answer
Hi Marvin, If the engine hasn't had a tune-up with plugs and wires or fuel filter change in 3 years or 36,000 miles that might be the place to start especially if the engine has over 75,000 miles on it. If this is the 4.9 liter engine take the distributor cap apart and check it for arcing/little rainbows around the wire terminals inside the cap. Past that you will need to install a fuel pressure gage and drive the car and see what the pressure does. Maybe the pump is weak. Then scan for codes and while driving monitor the data perameters and see if anything doesn't look right. Testing fuel injectors and coils for having weak spark are other tests that could be done. Other that changeing the plugs, wires and fuel filter I would expect that you would need to take it to a shop for the other tests. Hope that  helps, Bill