I have a 96 Disco that I was able to get back on the road about a year ago, after it sat dead for 2 years. I have replaced too many parts to count, including a new fuel system frm pump to injectors. It has a strange stall problem which begins after it has been running for around a half hour. During accleration from around 35 to 50 mph. It will cut out for 2 to 3 seconds then accelerate for 2-3 seconds, then cut out, then accelerate, etc. I can eventually get up to speed, but it takes a while. In addition, every once in a while, while it is doing this, the speedometer fails. Sometimes when the speedo fails, the truck runs normal. Any ideas?

Befuddled in Florida...

 

You did your own diagnosis. Speed is driven by the Vehicle Speed Sensor on transfer case. It also tells Engine Computer Unit (ECU) how fast you are going. That triggers an electronic governor to cut sparks and fuel to reduce speed. Supposed to happen at about 114 mph. When it goes bad, happens at regular speed.

The other thing that cuts spark is the CKP (crank shaft position sensor), but it does not impact speedo display. Usually fails and truck won't crank back up when hot.