88 GTA 350 my car always seens to run better when the check engine light comes on, and i cant figure the problem out. when the light is not on it idles up and down and at a stop in gear it jumps and wants to stall, but when your on the highway it runs great.

My question is how can i get the light to trip it so that it always come on.

when it comes on it runs light a brand new car. is there a sensor or a way that i could easily trip to make the check engine light come on?

 

the best way is to pull the codes and then fix what the problem is.

 

i tried, it doenst give me any codes, i thought i was doing it wrong and took it to a garage and they didnt get any codes either.

 

if the CEL comes on while driving, it should have stored codes.
does it at least flash code 12 when trying to pull codes?
if it doesn't, the ECM may have problems.