1995 jimmy 4.3L vortec cpi rough before warmup

My jimmy runs real rough for about the first 5 minutes, acts like it wants to stall. Then it clears up like nothing was wrong. After driving for about 10 minutes it then signals the SES light. BUT, it doesn't set a code. What does that mean? Vehicle has about 125,000 miles.

How is the tune up end/secondary ing and fuel pressure?
If light on it will have a code present or history.
Code may show problem.
Get it rechecked for codes present or history.
Post back code no.

If light on it will have a code present or history.

It set the SES light again. So just to check my scan tool I checked another car that also set the SES light. A code shows with the 2nd vehicle but no code shows for the Jimmy... still. Ever heard of anything like that? I double checked the vin #'s, etc. to be sure I was checking the right vehicle. Still nothing.

What kind of scan tool are you using?
What engine code?
OBD11 or other?

VCM or PCM computer?
95 is one of the years 3 or 4 different syatems used and some require a special 95 scanner set up.
You may need to get it on a good engine capable scanner for a 95 modle to test it out.

I use an Actron Super Autoscanner CP9145. I've used it on the Jimmy before and got codes but no codes this time. The scanner can do OBDI and II.

Check it right when light comes on before shutting off engine.
Does light stay on steady or just blink or flash on?

If the light come on there will be a code present past or in history.
NOT ALL SCANNERS WILL READ OUT HISTORY or PAST CODES.

NOT ALL SCANNERS WILL READ OUT HISTORY or PAST CODES.

I just read my daughter's trailblazer that stored a history; 2 different codes, with the engine off. Her SES light has been on for a while. (She doesn't live close enough for me to check it right away.) So I'm guessing this has something to do with the Jimmy. Next time it sets a code I will try to retrieve the code before shutting the engine off.

NOT ALL SCANNERS WILL READ OUT HISTORY or PAST CODES.

I just read my daughter's trailblazer that stored a history; 2 different codes, with the engine off. Her SES light has been on for a while. (She doesn't live close enough for me to check it right away.) So I'm guessing this has something to do with the Jimmy. Next time it sets a code I will try to retrieve the code before shutting the engine off.
Remember there is 3-4 different computer systems on the 95.
And they act and read and work different.
Good luck and let us know how it goes.