hey guys, i got a 98 ram 2500 5.9l gasoline that hiss under medium accel. if u full or 3/4 throttle it goes away or very light throttle it's not there. i read some forums about this too but i can't duplicate it. i called the dealer and they said that there's no gasket between the throttle body and the air box. i made sure the air box was tight and took it for a drive and it's still there. i even took out the air box to isolate the problem if it was between the air box and the throttle body and took it for a spin and the hiss is still there. as i rev the engine i can see the iac opening. it's closed at warm idle. i put a new iac in and doesn't fix the issue. the new iac made a whistle noise after throttle snap. any ideas? could it be new and old iac defective or throttle body bad?......and yes it sounds like a turbo hiss only that it's a gasoline.

 

Do you have the gasket on the TB?

 

How your plenum?

Always have to ask that....and you did say if there was a gasket for the air box, is there? Its a circle gasket you can get for like $2...if its cracked or missing it may cause the hiss you hear

 

yes i still have the throttle body gasket. and when i took the airbox off there was no gasket where the air box and the throttle body mates. i called the dealer to get one and they said there isn't a gasket for it(between the air box and throttle body).

 

also if i removed the air box and drove it and it's still there. that means it shouldn't be because of the air box and throttle body mates.

 

Dealer is full of crap. There is a gasket. About $2 as mentioned. Will make a sucking sound if it isn't there.

 

now if i remove the air box and drive it and it's still there wouldn't that tell me its not because of the gasket between the air box and the throttle?

 

no. Install the gasket and see how it sounds....

 

Without that gasket air gets sucked into the intake from the ring clamp dodad that secures the air cleaner box to the throttle body....