First of all, I already changed my fuel filter, spark plugs, pcv valve, distributor cap and rotor and throttle position sensor. I brought my car to a mechanic because at anything under like 3500 rpm the car had no power and was extremely lean. It was almost normal at WOT but something was missing and occasionally when I let off the gas after romping on it hard, it would backfire once really loud. I took it to the mechanic and he said my fuel pressure was all over the place and it was at 22psi. He set it back at 45(i have and adjustable fuel pressure regulator) and he said it was probly either the fuel pump or the brand new regulator I just put in was bad. How can I tell if it is the fuel pump or the regulator? I think it might be the fuel pump just because it feels like its getting no gas. HELP!

 

Put a vac/pressure guage on the fuel line check the readings before and after the regulator refer to the service manual for the proper ranges for your car. I believe that 45psi sounds about right. Check the computer for codes too.

 

The computer codes were checked and none came up. When I turn the key before I start the car, the pump doesnt really prime right anymore. It either does nothing or makes a weak noise. Plus, how can a regulator just randomly go bad? I dont understand. And also, when my car isnt warmed up, it runs better and seems to get more fuel, and under full throttle it gets more fuel. But other than that, the car is always lean. It doesnt make sense.

 

First question: what is telling you that it is lean?

Second: Do you now maintain 45 psi at WOT?

Third: Have you checked all of your injectors for proper operation?

Before you drop the tank (it's a royal pain in the butt), try to do as much to eliminate the possible problems in the engine compartment.