ah Professor,

is this happening with all planes or just specific ones?

If you wiggle the throttle does it fire back up again.

You have to be carefull with engine management when you warp. The game still runs the engine at your last setting as if you had flown the entire warp at those settings.
Therefore if at full throttle and full prop pitch you may well run out of fuel along the length of the warp. Check that the selected tank is not empty.

If you have changed altitude during the warp you may need to adjust the mixture/prop settings.

I'm not sure as I don't warp much but if it is a 1% plane with RX you may have over heated the engine during the warp. I seem to remember reading that somewhere.

Diving would increase the airflow over the engine and may allow it to get going again.

Just ideas as I haven't had this problem myself but as I said I don't warp a great deal. I don't fly too many missions but I think getting there is half the challenge.

Find out where the waypoints are and add them to Nav3 then use paper, pencil, ruler, protractor and the planes compass to navigate there. Just like the real guys did. Oh, and turn of the tactical display, obviously!

Not always viable if it is a 2 hour flight to the next waypoint as real life has a habbit of getting in the way!
Once I think I'm going in the right dirrection I can increase sim rate to get me there  but quicker but you have to keep an eye on the compass.