Tapping

Hi

Any advice suggestions would be grateful please.

My son has been borrowing my car, apparently when he went down the road he felt like the car lost a bit of power. He came into see me and on leaving again, he noticed a slight sort tappy noise. he drove down the road for me to hear then there was a slight sulphery smell and it was definatly making a strange noise, almost juddering. I cannot get to speak to my mechanic until tomorrow but am seriously worrying. In my limited knowledge the only thing I could think of was maybe a head gasket from things I can remember from the past. Though he wasn't sure whether it was getting overly hot!!

Many Thanks.

Nikki

P'S Have just read something on here about coil packs? it has sometimes not wanted to start first turn but this has not been a regular thing but occassionally.