Hi New here and technically ignorant ! My diesel Disco 1997 jap import when driving and building speed is surging off on off on with power and as speed increases around 90 t0 100 kms per hour seems to settle down to drive ok .
I changed the air flow censor with an old one and it seemed to run ok for half a day then went to it again ?? what are the possibilities to fix this .
many thanks for your ideas

 

Did a live data check and only note the minor change, no big jump in mph. Disconnected the VSS and the issue continues.
the only other factor that may be relevant is I had removed the purge valve since it wasn't working. I doubt it's an effect as the problem started much after.