Land Rover Repair: TAPPING NOISE FROM THE ENGINE AND POWER LOSS!,PLZ HELP, rangie, valve job

Question
How you doing sir?,well i have a range rover 1996 4.0 SE (unleaded fuel),its been a year now since  i got the truck,recently about for the last 3-4 weeks it started making a noise(sounds like a tapping noise)from the engine,and the noise doesnt change when the truck is cold or warm,increses as i accelerate.Now for the past two days the car sounds like loosing its power when i  reach to 50 mph ,i thought was transmission but i doubt beacause the engine doesnt go above 25000 rpm how ever much i hit the gas, instead just getting stuck there on 2000-25000 rpm or on the gear 3(i have no problem with gear shift 1-2-3 in this situation),and this only happen when i just come form warming up the truck after sitting on parking lot for couple hrs,but after i drive for couple minutes the engine doesnt seem to loose power like its been soften or became light ,its not the normal way like any car does when the engine is cold the gears become heavy to shift this is kinda different , so please coild help me to identify what the is the problem before i take to dealership for check up ,atleast i should have idea what it is ,instead of me guessing may be manifold,lifter or gasket and other stuffs,i will appreciate your help,thank you!

Answer
Hi Tonny J,

what fuel are you using?  Make sure it complies with the fuel type needed for your Rangie.  Here in N.America, the fuel you use should have an octane minimum of 91.  Anything lower and you'll hear noises, much like what you've described to me.

Its possible that your 4.0 engine has some exhaust valve problems.  Carbon deposits have been known to buidup on the exhaust valves, causing them to stick.  This can rob you of power and performance.  Its most often noticed on hot, humid days and when the engine is fully warmed up.  The only cure is a valve job.

Just make sure all the fluids in your Rangie are flushed and new.  Use the best fuel you can find locally, keep an eye on the engine temperature.  If you don't think its the fuel, you'll have to mount your engine with a testbook diagnostic tool to reveal any problems.  You could buy an OBDII reader to see if there are any codes being trapped but an experienced mechanic may have to fully diagnose your engine management system (EMS).

I hope this helps,

JohnMc