After driving for a while, in hot weather, 85+, with AC on and car at idle (breaking for stop or yield sign)bell rings and dashboard sign reads “stop engine now”. As I increase RPMs, bell and sign stop and car performs normally. All fluids are OK and oil pressure switch had been replaced. What’s causing this behavior?
What kind of Caddy? Have you checked the codes? (do you know how to read them from the dashboard?)
DeVille Coucours No No
Then go here to find out how to check the codes: http://www.cadillacforums.com/forums/cadillac-tech-tips/55172-how-pull-codes-got-codes-warning.html
Pull the codes, and post back with your results (the actual codes). Make sure you take a pen and pad of paper into the car with you - the codes go by quick.
I believe the “stop engine now” light comes on in two situations-- overheating and low oil pressure. Unfortunately the symptoms you describe sounds like the notorious “flickering oil light on the off-ramp” issue. This is usually an early sign of bearings that are wearing out, which will eventually mean an engine rebuild or replacement. Switching to a higher viscosity oil will probably make the issue go away, but it will only be delaying the inevitable.