Strange engine problem, need some help Options

[Joram]

Since a month or so I have some problems with my engine. I have a AT200, with a 7AFE from 1994.

This is very hard for me to explain it in English but I'll try my best.

Sometimes it seems like my engine doesnt get any fuel for a second and then it runs normal. It just suddenly drops in RPM and less then a second later it runs normal. It's kinda like a shock. And when it begins it doesnt stop shocking. Until I stand still. When my RPM is around 1000 and it drops, then the motor stops.
When I start again, it runs normal again.

This problem isnt always there. The car was at the garage and it run perfect for about a week. Then it begun again. Then when the mechanics at the garage drive in the car it runs normal. They are now searching and searching, but no succes. The problem is that the problem isnt always there. You can drive 150 km without troubles. And later you start it and after 5 km it starts shocking.

Does anyone have a clue about what could be wrong?

Thanks

[Joram]

well, it does it too often too not worry about it. The mechanics at the garage have already looked at the ''normal'' things, like ignition and fuel filter.
It must be something else.