Chrysler Repair: 1990 Cadallac DeVilles got the shakes, throttle position sensor, emission control system

Question
I own a 1990 Cadallac DeVille that has 150,000miles on it that has been running fine.Recently after driving for an hour or so ,it idles good at stop light,but wont pull out,and lurches and bucks when I try to give it gas.If i put the peddle to the floor it bogs down and won't go,but will idle again fine.any suggestions? Thanks

Answer
Hi Robert,
You are asking the wrong "expert" on about your Cadillac. I really have no knowledge about the GM line of cars. In general, I would suspect that it is a problem with the fuel mixture side of the equation rather than the spark control or the mechanics of the engine proper. Maybe there is an electrical open spot in the throttle position sensor's variable resistor, or there might be something wrong with the engine vapor emission control system, or a vacuum leak in the line from the intake manifold to the manifold absolute pressure sensor. I assume that your engine has all those components, but I really can't be sure. But if anything in the fuel supply is being mishandled then you won't get the appropriate mixture and thus the stumbling on start up. Why is should begin when the engine is warm is an unknown, but may be relevant. There is also a coolant temp sensor that adjusts the mixture as the engine gets warmer, but if that were acting up it should show up as a problem sooner than after an hour. You didn't say how it runs once you get underway again. Does it continue to stumble when you have it up to a moderate speed?

There is probably a way to readout any fault codes that may have been observed by the engine controller that you can do yourself with the ignition key, but you will need to seek out a GM expert to tell you how and to provide a code table to translate the code number into something useful.
Good luck with this, but I am just totally incompetent on GM cars.
Roland