why does my 1986 plymouth reliant run smooth with the power loss light on and run rough when the light is off.

Question

the battery stays charged either way

Answer 1

Because, when the light is on, the computer changes its values, or parameters to go into a "LIMP IN MODE." What this does is it will give fixed values for the computer to get the car to a dealer for repairs. When the light is off, The computer sees no problems. So you might have two different problems. Might be as simple as a tune up for the engine off problem.

ASE TECH 25yr