i just finished a timing chain kit replacement...4runner runs fine with no leaks....but i have a hissing niose comming from the air filter...when i take the it off at the throttle body the runner dies....any ideas what would cause this ...thanks
oh ya it's an 88 4runner with a k&n air filter, never made this noise before...

 

Its been covered here many times... But when you pull you intake tube off, you're closing the VAFM, which in turn shuts your fuel pump off. You have to find the noise with it connected, or the engine off.

 

thanks carl....ya i looked throught the search engine (air filter hissing)..but couldn't really find any thing that explained the noise...
I did have retarded timing when brought to T.D.C before the timimg chain replacement...now mechanical timing is good ..and have to turn down idle from 1000-750 rpm..have yet to check ignition timming..(dont know if any of this has anything to do with it..?)
Ill have to check vacume lines again.....
Or is this just how these k&n air filter kits with the big cone shape filters sound (P.O had it installed).. thanks brock....

 

I had a similar sound when i redid my timing/headgasket. found that i had the vacuum lines to the vsv thing on the valve cover hooked up wrong and made a good hissing noise. if i remember it has two vacuum lines going into it and it sits in the center right hand side of the valve cover. hope this helps

 

It's probably just the k & n kit. However you can run an UNLIT propane torch along the intake tube and all vacuum hoses to check for a leak. Anywhere it idles up, you have a leak.

 

If your running an open air filter, your going to hear a hissing sound. That the air being drawn into the air filter.

 

Yeah, I meant the stalling when disconnecting the intake...coulda been more clear on that.

 

You can`t disconnect the intake at all when the engine is running. Air has to pass through the AFM for the engine to run, and the AFM also turns on the fuel pump, so when you disconnect the intake the engine will stall.