Will a faulty oil pressure sender or low oil level indicator on an 87' 5.0 cause limp mode or are they just for guages and dummy lights? What else can cause limp mode? It only happens after about ten minutes of driving.
I don't believe that the oil sender will trigger anything like that, but I know that if the engine begins running too warm that the computer will pull timing. What you describe sounds like bad 02 senor(s). Both of mine are actually bad, and I will get a check engine light after approximately 10 minutes of driving; the car essentially will always runs in open loop without the 02 sensors and will not run as well as it should.
Off topic, but is it true that having the check engine light on will send it into open loop? Mine is on because my EGR is disconnected. I had one of those egr eliminators hooked up, but it fell off and got lost. I noticed my gas mileage is down to 17MPG, but I'm not sure if thats my driving or if its because of the engine code.