My 97 discovery's check engine light is on the automotive shop said to replace cps, plugs, wires, and might be coil packs. I've done all of that and the check engine light is still on. Here's the problem the lights surge, lack of power, tach jumps around, and engine lobes slightly. Doesn't miss under acceleration, and also the speedometer has dropped to zero under driving conditions and then gone back to actual speed. Check engine light will go on for a few weeks and then mysteriously go off for a few days, and then come back on. HELP!!!!!! Any suggestions are greatly appreciated!!!

 

Man to bad you didnt come here first.
Speed Sensor / Transducer - Vehicle - Road - Vss | Land Rover Electrical Parts, Batteries, Relays, Lamps & More
Your VSS is bad, when it goes bad it sends a false signal to the ECU and the ECU thinks you are exceeding the top governed speed for the truck (110 mph) and then cuts spark to the engine to slow you down.
Thus the rough running, lack of power etc.
The clue is the speedo dropping to zero.

 

I have a parts rover to pull from so it only cost me the $38 for the cps and the new plugs and wires, which it needed. Then what would cause the lights to surge constantly and the tach to bounce around.

 

The lights to surge and the tach to bounce are a bad alternator or a loose connection on the back of the alternator.
And make sure the belt is routed correctly, it can go on several ways and only one is correct.
In the tech section of the DI page there is a diagram of the correct routing.