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.

I have a 97 vortec 454. When cold it starts and runs good, but after it is warmed up it will idle rough. Also when cruising at highway speeds it will shudder or buck every once and a while. Plugs and wires seem good. No vacuum leaks that I can find, changed pcv valve, and fuel filter. Not throwing any codes or check engine light.

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.

My engine runs really rough at idle. Seems to smooth out as I accelerate. Check engine light comes on and off intermittently. Do you have a vacuum hose diagram?

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.

Truck seems to idle fine, but the more you drive it the worse it runs. Service engine soon light appears when engine reaches normal operating temperature. I have replaced spark plugs (with OEM plugs), plug wires, distributor cap, distributor rotor, fuel filter, air filter, thermostat (was stuck open), inspected all vacuum hoses, thoroughly cleaned throttle body and checked for water in the fuel tank....... I am stumped can you please give me some insight as to what my problem may be?

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.