what could be wrong with my hdi?

[Josh1994]

Hi all,

So i just started the hdi up after a month and a half, good thing is that she started up. Bad thing is i think something is going to go wrong with the car. When i started her up the revs went to 500 revs under 10, and now keeps revving up and down slowly, never use to happen before.. could this mean it could be the EGR Vaulve? Same thing happens to my dads 2008 ford transit..

Any advice?

Josh..