99 Explorer starts, but no idle

My -99 Explorer V6 4.0L SOHC starts if I give some gas and keeps running, provided I keep giving gas. But as soon as I let go off the pedal, the engine dies. Clean as if I would have turned the ignition off.
I've checked the IAC and the TPS and the values are spot on according to the Haynes manual.

There is a hissing sound that is fluctuating a bit with the rpm and fades away once the engine stops.

Any ideas, please? You guys wouldn't believe the workshop prices here in Sweden for such a car.

I had a same problem with my 2000.  I had the replace the manifold gaskets which solved the problem and started and idled no problem

Thanks,

I took the opportunity to replace the cam chain tensioners (before it starts to rattle). As part of that process, the manifold is off and I replaced the gaskets. They were indeed dried out and well overdue. Unfortunately, the idle problem remains although there is now an effort to stay alive. Maybe there is a crack in the manifold somewhere.

Maybe it's time to bring in the pro's after all.

G`day friend
    Just brought a 1999 explorer with what sounds more like noisy lifters
do you know if they suffer froms this or is it tensioners ?
What sort of cost would i looking at ?
Cheers
Roger

The noisy lifters is probably the timing chain tensioners.

jnorback sounds like he has an intake leaking or a vacuum line or PCV line is leaking. Listen real close for the hissing sound and you will find it.