So the problem I am having in my 99 Disco 2 with the 4.0 and an automatic trans. is that just out of the blue one day I went to go take off from a stop light and it took about 300ft to get up to about 3k rpm's and then it just takes off. at high rpm's it seems to run just fine but does seem like the timing is off but like I said it just sporadically happened one day when going to take off from a stop light. And did not happen every time for the first day. after that it has been like this. I have replace the tps so far, fuel pump and filter. tune up. starts every time but It does not idle. I can keep it running for as long as I want as long as I have it above 3k. it doesn't have any codes on the obd 2 as well.

 

Your code reader is broke!

Seriously though... With those symptoms... I'd check your transmission fluid level. It sound like more of a transmission and shifting issue than an engine issue. Get a code reader that will read more than just OBDII. I think i have an icarsoft 930? Think I paid around $60 on amazon.

You need to go deeper than OBD2 if you are having issues like that without a CEL. I'd check the transmission fluid first though.
Edit:
Sorry... didn't exactly understand that you HAD to keep it above 3K rpms. So... now we're back to the broken code reader.... or you haven't driven it enough to pop a code yet... but that's a stretch. Check for a vacuum leak in your brake booster line? Investigate wiring to knock sensors? Clean your Idle Air Control Valve. For now... I'd assume either your ECU is screwed... or your OBD2 port is messed up.