bought the car used couple of months ago in the winter
when weather gets hot, the engine have problem starting. changed the main relay by someone
starts better now, but problem still happens restarting after 10-15 minutes drive once in a while.
then there is another problem, after 10 15 minutes of driving, 5 speed, and the rpm will surge up 1000 rpm itself when driving, rpm come back down, then it will idle roughly, up and down 300 to 800 rpm @ idle. check engine light comes on, and engine lost all the power. the next morning it will work fine again!
thanx in advance.

 

When you get a CEL what is the code?

Have you tried these:

Checking dizzy
plugs/wires
Run some bg44K through the fuel system
air filter
clean iacv

??

 

it's a friend's car actually. it's an old car, i don't think those tuneup has been done to the car.