All of a sudden my 4x4 cos will lose power and backfire rpm meter races up and down then regains power again.

Colud this be tps? Map sensor?

 

with the rpm needle going up and down eratically coupled with a misfire is a sure pointer to the coil end of things or the ignition amplifier,the green wire comming off the coil goes to the rpm clock and so many coil pulses equals so many revolutions,if the coil pulses eratically it will show on the rpm clock and its the ignition amplifier which plays a part in this but doesnt actually tell it when to pulse.but they can give trouble and are an easy fix
another cause can be bad earths on the inlet manifold and elsewhere on the engine,also the 3 big block connectors at the back of the engine bay are also known to be a cause of this problem,have a check of all the engine earths and open and close the block connector a few times to make a good connection and do the same with the ignition amplifier connector

 

It could be:- Your boost is up too high and either the turbo is shitting itself or there is a spark problem, when was the last time you changed your plugs? and are they decent ones?

 

Thanks velocity will have to check that out its very tempermental, and does wether on boost or not the engines just been built

 

check the connectors on the bulkhead......the 3 big ones...clean them and tight them real good....

better solution....cut them away...and soldeer the wires....

 

yep. the three connectors are prime candidate especially the one nearest the battery with the larger wires in.. but failing that, velocity is all on the right track - check all ground connections to the battery, engine block and inlet plenum, as well as making sure the connections on the coil and ignition amp are clean.

 

It was the distrubitor senser the two wires had melted the insulation off of them