Spasmodic car problem. Any Chevrolet experts out there?

Question

1998 Cheverlot Lumina 3100 engine all power. Problem comes and goes, no check engine light. After starting engine it idels smouth. When giving it gas, it starts missing and back firing only when engine is cold. After it warms up problem is gone. Yesterday it missed like it was running on 2 or 3 cylinders. Just before problem cleared it made loud knocking sound like a rod, clack clack clack about 15 times. It's full of oil. I have noticed the problem is worse when the humidity is very high or after a rain. The car is kept in a garage, so it doesn't get wet. Please if you don't know say so, I don't need wild hair brained guesses. And yes I have changed the fuel filter, oil, and air cleaner, plug wires and plugs. I would be gratefull for your help.

Answer 1

Your fuel pump is worn out and not delivering enough flow AND pressure.

When the engine is cold, the computer runs in preset mode and does not use the O2 sensor for emissions, fuel mixture, timeing, or EGR control. So it's NOT any of those.

Also, when the engine is cold, it needs more fuel than a hot (warmed up) engine. The need for extra fuel makes the fuel pump work harder trying to deliver more fuel.

Unfortunately for you, the fuel pump is inside the fuel tank and the tank needs to be removed to get to it, and can be expensive to replace.

Any good auto repair place should be able to flow, and pressure test your pump fairly easily to make sure that's the problem BEFORE replacing the pump.

Answer 2

Take it to the broker and function it regarded at, you have a guaranty, use it. additionally, have you ever had the recollects accomplished on your vehicle, i think of there have been a minimum of two for that 3 hundred and sixty 5 days. One had to do with gasoline strains, which might join the priority.

Answer 3

might have a bad computer, go to autozone and have them read the engine codes for you. they will do for FREE. never know check engine light might be burt out.