My 91 caddy started running rough today.

I am not getting black, blue, or white smoke at the rear.
Timing light lights on all 8 wires
Gas mileage went to hell
All seams to be in order with the the fluids
Small squirts of starting fluid around the top of the engine produced no signs of an air leaks

The only thing I can get out of the climate control unit is "f80" or "f.8.0"

Any help would be appreciated
Thanks
Chris

 

Any help?

thanks
Chris

 

If there are no E codes then you should start with the basics: Fuel, spark, compression and timing.
I usually inspect all spark plugs when investigating an engine performance issue.

F.8.0 is BCM data , it shouldn't even show up until ecm codes have been displayed