While driving one of my hmmwvs it started to kind of hesitate at around 40mph it acted like it had died but was still running and lost all power.while slowing down the engine would surge a little jerking the vehicle losing power and regaining it. Only does this when the engine is hot I got home tinkered with stuff and took it back out ran great till it reached operating temp. any ideas what this may be I already got a fuel filter ordered. any input would be appreciated this particular truck is full of gremlins that keep on suprising me.