I have a 1990 S-10 2.5l FI 2wd. It starts and runs fine for a while. Then starts jerking and bogging down till the check engine light comes on. Then it runs fine. The light almost always comes on going up a hill. When the light goes off it starts running crappy again. I am getting codes 42 & 44.

Thanks for any help.

Code 44 is lean exhaust.

Code 42 is a short or open to ground in the HEI-EST or bypass circuit.

Does both codes come in same time?

Not sure. I will clear the codes and then check it again after the light comes back on. Is that the right thing to do?

Yes that is a good start.
But if either code comes back get a good repair manual and go threw the repair flow chart for that code.

On the lean exhaust code make sure the fuel pressure is up tp par and check fuel filter.