Land Rover Repair: Land Rover Discovery shudders at 70MPH and up and check engine light comes on, land rover discovery, scan tool

Question
I have a 2000 LR discovery and lately, when I hit 70 MPH the car will shudder and the check engine light comes on.  Usually, after the car has been resting and cools, the light will go back off, but sure enough if I get up to 70MPH it will start flashing again and stay on until the car cools again.  I'm not in the position to be testing/changing a lot of parts so any insight as to what may be causing this is greatly appreciated.

Answer
If the light is flashing that means you have a serious problem that will result in expensive damage if left unrepaired.  Connect a scan tool and see what codes are stored.  Chances are, you have misfires.  If so, you need to determine if you have bad plugs, wires, injectors, etc.  The live data stream on the scan tool is essential to do that.