I have 1989 s-10 pickup with 2.5 4cyl. Sometimes

This does happen a lot if the spark plugs are worn out or the type of plug altogether is wrong. The plug might be struggling to keep sparking if it is worn out or the elctrode gap it too wide on the spark plug. Have a look at the car manual to learn more about the spark plug but also Have a look at the ones already in the car and see if they are the right ones recommended in the manual and also check if they look worn out.

I hope this helps you in some way. Good luck!