Engine problem

When the Check Engine light turns on there will be at least one diagnostic fault code stored in the Engine Computer. Many auto parts stores will read them for you for free. That's the place to start. Those codes will lead you to the circuit or system with the problem, not necessarily the defective part.

Based on the multiple symptoms, you might suspect the generator. GM has a real lot of trouble with them. They often develop excessive voltage spikes that interfere with sensor signals for the many various computers. As a test, you can unplug it then see if the engine runs better. If it does, have the generator checked. It is real common to go through four to six of them in the life of the truck. What many professionals are finding out is to reduce the repeat failures, you should replace the battery at the same time. It will still work fine in older cars from before 1987 but as they age they lose their ability to dampen those voltage spikes.

Caradiodoc

Hello,

Two things come to mind, first s a vacuum leak which you can find out by following this guide.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

The next is old spark plugs, have you replaced them recently?

Here is a guide to help you get the problem fixed.

https://www.2carpros.com/articles/how-to-change-spark-plugs

and

https://www.2carpros.com/articles/engine-vibration-at-idle

Please let us know what happens.

Cheers, Ken