Timing delayed

I have a 96 olds 88 with a 3.8 series II engine. Fuel consumption has increased lately so I hooked it up to my scanner. The scanner shows that the timing is way delayed. at idle it shows -18 degrees. driving it can go as far as -30 deg. It seems to run alright. A little more exaust noise like it would be with delayed timing.

What could be causing this? Crankshaft position sensor, Knock sensor?

Any help would be much appreciated!

Jim

I don't think you are getting accurate info, -30 would cause the engine to fall flat on it's face.