1990 No Up Hill Power?

[Ripsaw]

Originally Posted by ChevyTech

It sounds like there are many problems with this vehicle.

A cylinder that misfires needs to be repaired.

Here is how a misfire can affect the system:
These systems work great when every thing is right but they have a big flaw. Once the engine misfires for any reason it throws the system in the rich direction. This system watches the O2 sensor, but the O2 only will see how much oxygen is in the exhaust stream NOT burnt gas. When every thing is right the O2 knows just how much of the oxygen should have been burned by combustion. If the system gets a little to rich all oxygen is consumed. If it gets to lean there is not enough fuel to burn all the oxygen and there is more oxygen in the exhaust. Once it misfires, there is way more oxygen in the exhaust, because none got burned in a cylinder. The system thinks it is to lean so it gives the engine a richer mixture. The richer mixture often makes it misfire more (especially if it is cause by weak ignition, bad plugs…) so it dumps in more fuel. Now it is so rich the plugs and O2 sensor get soot on them. It misses more. The system goes richer and richer.

Great explanation, thanks !