oil is new and full,during idle oilpressure drops and engine idles rough, stalls

Thanks for your help,Globalhelper, I just purchased this Buick. I need to know the true condition of the engine,if there was odometer tampering,is there an engine diagnostic that will tell me the true state of engine health? I don't want to just start changing out parts on a wild goose chase...this oil pressure issue could mean an engine overhaul and this is frightening.What is the cost of diagnostic? If engine needs overhaul, what is that going to cost?

take it and get a compression test and leak down test to determine the condition of the motor and ask alot of questions prior to getting diag. ask for oil pressure test a motor could cost upwards of 3500.00

My 1992 Buick Roadmaster Estate wagon has 50,000miles, has a slight idle tremor while stopped.At first it would idle under 500 rpm's and the oil pressure would drop below 20, then eventually stall, while I had my foot on the brake. If I placed in neutral the idle would be a bit better, but could still feel the tremor. I replaced old sparks with new, the tremor is better but noticeable.Could it be the timing chain?, what is the cost of repair?

It sounds like you could have a vaccume leak in the brake booster sys.