And this is not just the cai/intake sucking hiss either..

Here's the scenario - I can gun it in first to about 25-30mph.. then I'll shift to 4th. When I hit the gas, I hear a huge hissing from under the car.. "psssssssttttttt", and it slightly pulsates. THe car hesitates a bit while its hissing, but after 2k rpms, the hissing starts to go away, and by 2.5k-3k rpms, the car doesn't hiss anymore and starts pulling normally. The more I push in the throttle at low rpms, the hissing is louder... and the car feels gutless. This happens a lot in 6th gear as well - it happens loudest when I am at a high throttle position during low rpms.

Its annoying as hell and its been driving me nuts since last year. When I drive, it sounds normal, but once I get next to a car or wall, the hissing bounces off, and its LOUD.. very unpleasant, and definitley not normal.

please, help me get rid of this problem! I've tried spraying carb cleaner/wd40 around vaccum hoses to see if its a vaccum leak, but.. that doesn't seem to be it..

perhaps an exhaust leak?

possibly - its been happening since ive had my headers on.. but doesn't it make more of a ticking noise, than a sucking/hissing?

is it like when u realese the clutch the rear end kicks?
and hesitates and then its normal??

Have you removed your intake elbow and inspected it for cracks? Maybe your whole intake system should be checked over. It may take a certain amount of vacuum to make it apparent and there is not enough at idle to detect it.

shoebox, i've checked the intake system, and they're all bolted in good, no cracks, nothing.

I'm checking the rest of teh vacuum hoses and pcv hoses and such tonight. One interesting thing to note is that a little bit of oil has puddled up on the intake manifold, right below the brake booster vacuum. I'm going to check for vaccum leaks around the pcv lines, I guess.

is it possible for an exhaust leak to cause a hissing/whoosing noise, or is that a dead giveaway that its a vaccum leak?

(oh and when i let the clutch out, its already hesitating. I had trouble breaking the tires loose even during rainy weather...)

It could be an exhaust leak. I had a vacumn leak on the little rubber boot on my EGR... you could hear it at idle but once you get goin the exhaust and road noise handles it. If you had a big leak i would say yes, but it sounds like an exhaust leak. It usually taps and clicks but the symptoms are those of an exhaust leak.

thats just how headers sound dude, same thing happened when i put mine on, i like the noise, sounds smooth.

nah, this hiss bounces off walls and is loud as hell.... makes the car hesitate only while it hisses, but once the hissing stops, the car seems to get up and go a bit better.

anyone know how to tell if this is vaccum or exhaust? I'm planning on taking this into a shop tomorrow or friday, to have the exhaust leak possibility looked at...

thanks to all those who have replied so far.

hmm, maybe your AIR pump is f'ed up?

Check all of your plugs... make sure they ar e all in tight! The hissing sound that you are hearing could be air spitting back through the very small gap between the plug and the head... I know it sounds stupid, but trust me, it is possiable!


You don't want to let it go on for too long if that is what it is. Because one day you could be driving along, minding your own buisness, then get on it a little to get over into traffic... And <CLICK CLICK BAM BAM CLICK> it will sound like a rocker slipped over to the side! Sounds very bad! It will be that one plug that wasn't in all the way... It will have been blown out of the head!


Just had that happen to me not too long ago! But I fixed it in about one hour!

air pump and plugs..

thanks guys, i'll give those 2 a good look over tonight!

now tight should plugs be? I've kept them somewhat loose because I'm afraid of stripping out the heads.. but of course, i'll go over plugs today. sounds very possible.

thanks, guys, i'l keep you posted.

You are not going to strip them out of the head unless you use like a one foot breaker bar and keep tightening, lol.

Disconnect your serpentine belt and start your car.

That will eliminate any of the accessories.

Also check all your EGR and vacuum line fittings on the intake manifold.

Did you reconnect the airpump to your CAI?

Do a vacuum integrity test on your EGR and it's vacuum lines. Could be that you have a split in the EGR diaphragm and that is why the sound it not always present. The EGR operates in part throttle situations. Just a theory, since it seems you have found nothing, yet.