My engine runs rough?

Misfire can be a hard item to trace, however an easy way to determine which cylinder it is would be the old cylinder drop test. Use a pair of insulated pliers and pull one plug wire at a time and listen for the engine to change how it is running. When you pull a wire and nothing changes you have the cylinder with the problem. These guides can help us fix it

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

and

https://www.2carpros.com/articles/how-to-tune-up-a-car-engine

If good spark - Time to check the injector unit for stuck or damaged poppet or injector, Depends on exactly which engine you have.
Please give us that information.

Hello,

This sounds like you have an engine coolant sensor that is shorting when warm which is common her is a guide to help us find the problem.

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

Please run down this guide and report back.

There are dozens of vacuum hose routing diagrams in the service manual that cover every optional system and engine size. To be sure you use the correct one for your truck, it is shown on the emissions sticker under the hood.

The best suspect for misfires are the spark plugs and wires. You need to read and record the diagnostic fault codes to see what the engine computer has detected. Here is a link to the procedure to do that yourself, and the code definitions:

https://www.2carpros.com/articles/buick-cadillac-chevy-gmc-oldsmobile-pontiac-gm-1983-1995-obd1-code-definitions-and-retrieval-method

I can interpret those for you and give you some ideas of things to look for.

What you need to do here is have the computer scanned for code/s -you have a problem within the engine management system causing the SES light to come on.

https://www.2carpros.com/articles/buick-cadillac-chevy-gmc-oldsmobile-pontiac-gm-1983-1995-obd1-code-definitions-and-retrieval-method

Or you can try checking the throttle position and manifold absolute pressure sensor to include a fuel pressure check.