I have an 87 oldsmobile delta 88 royale brougham and I have a dianogistic done to it and the car would just die after 15 minutes at idle. The mechanic said it was the ignition control module. So I replaced that along with the 3 coils and let it run for about 15 min and it died again. Does anyone know what else could be the problem? Someone else had mentioned an idle sensor? If that's the problem, where is that located? And do you have to do any adjustments to the module or coils?

I see that someone said that it is the EGR valve. I don't think that is the problem at all. What size engine is in this car? I mentioned before the coil is usually the cause of the car to start and run till it gets hot, then die and not start again till it cools down. This is a coil problem 99% of the time. And I will explain why. A coil is nothing more than the name. A coil of copper wire inside the coil. When copper, like any metal heats up it expands. And when it cools, it shrinks. When the coil gets hot, the copper expands and the wire in the coil separates. And the coil quits working. When it cools, the wire makes connection again. Letting the car start again. I was thinking that this car had HEI ignition. Which only has one coil. But I could be wrong. Don't work on a lot of these older cars much anymore. I would check the spark on each individual spark plug and see what you get. I bet that you find that you are not getting spark on 3 of the plugs. I see that someone said that it is the EGR valve. I don't think that is the problem at all. What size engine is in this car? I mentioned before the coil is usually the cause of the car to start and run till it gets hot, then die and not start again till it cools down. This is a coil problem 99% of the time. And I will explain why. A coil is nothing more than the name. A coil of copper wire inside the coil. When copper, like any metal heats up it expands. And when it cools, it shrinks. When the coil gets hot, the copper expands and the wire in the coil separates. And the coil quits working. When it cools, the wire makes connection again. Letting the car start again. I was thinking that this car had HEI ignition. Which only has one coil. But I could be wrong. Don't work on a lot of these older cars much anymore. I would check the spark on each individual spark plug and see what you get. I bet that you find that you are not getting spark on 3 of the plugs.

Replace the crankshaft sensor. Replace the crankshaft sensor.

This may be a job for a shop. It's not that easy. You'll have to remove the crankshaft pulley. This can be difficult if you have not done this kind of thing before or don't have the tools. After the crankshaft pulley has been removed, you'll see what I mean about using the match stick. The sensor has two halves that go on either side of a circular vane on the back of the crank pulley. The vane must be spaced in the middle of the sensor. The crank sensor has an adjustable mount. You mount it loosely and put the crank pulley back on with the paper match bent over the vane so that it centers the sensor, then you tighten the sensor mount. This may be a job for a shop. It's not that easy. You'll have to remove the crankshaft pulley. This can be difficult if you have not done this kind of thing before or don't have the tools. After the crankshaft pulley has been removed, you'll see what I mean about using the match stick. The sensor has two halves that go on either side of a circular vane on the back of the crank pulley. The vane must be spaced in the middle of the sensor. The crank sensor has an adjustable mount. You mount it loosely and put the crank pulley back on with the paper match bent over the vane so that it centers the sensor, then you tighten the sensor mount.