Land Rover Repair: Land Rover Disco Power Troubles, land rover discovery, irregular intervals

Question
Land Rover Discovery 1 4.0 '98 LSE  73K.  Recently purchased 5th owner.  It is in very good shape.  In very irregular intervals while driving 55+ the engine looses power for a brief second or two.  This will contiue for 5-10 cycles every 10-15 seconds and then run ok.  This just started up and the check engine turned on in conjunction with this.  My first  guess would be fuel filter (I do not know when it was changed last).  I do not know a lot about engines but have change manifold and vaule covers with the help of a Haynes.  The only manuals I found were the $120 shop manuals.  I do not have the $ for the shop.  A customer of mine sold this to me for a steal with the warning "they  cost a lot to repair."  Sorry I ment this to be brief.  Thanks!

Answer
Intermittent cutting out like you describe is often the result of a bad speed sensor (on the transfer case) or a sticking valve in the engine.

Look on the robison service web site under service dept > land Rover > advice for the sticking valve article, it goes into much more detail.