a couple of questions about the idle screw.. the idle screw causes a vacuum leak that rises idle depending on the leaks pressure correct? a vacuum leak can cause hp loss correct? i also notice the tone of the intake rises the more i loosen this screw.. what is the cause of this? so if my question about vacuum leaks causing power loss is right.. what if we can tighten the screw til there is no leak and get the car to idle properly with hondata, etc.? i know you guys are thinking your not suppose to mess with the screw but it has already been tampered with b4 i got it. and i know your suppose to unplug the iacv and set the idle at 450-500 then plug it back up but i am still curious about my theory. what do you guys think?

 

The cars RPM is determined by how much air bypasses the throttle plate. The idle screw is tapered so it lets in more air as its screwed out.

That's why the RPMs increase if you have a vacuum leak. I cannot see how a vacuum leak can hurt performance but I could very well be wrong.

You setup your idle speed by disconneting the IAB valve and turning all electrical loads off, as idle RPM is affected by how much the engine is being loaded by the alternator.

 

Vacuum leaks cause problems when they are large enough to dilute the post combustion gasses read by the O2 sensor. The sensor sees this as a lean condition and increases injector pulse width to compensate. It also reduces the vacuum available to EGR, MAP, Fuel pressure regulator and so on. The amount of air let in by the idle screw was there by design and to small to be significant to performance.

 

very true. i agree with the last post. idle screw will not kill performance. but a vacuum leak will be enough to throw off manifold absolute pressure and cause performance problems.

 

good help guys. was just wondering cause the intake gets louder everytime u keep unscrewing it and sometimes it feels like it accelerates a lil better than with it tightened all the way. but it could be all in my head who knows lol

 

I just installed a 70mm throttle body on my type r and the car is idling irractly. Sometimes it idles at 1500 rpms and sometimes it idles at 100 rpms. I've adjusted the idle screw and it ends up throwing a light for the fuel system being to rich. I've thought about just putting the stock throttle body back on to see if this corrects the problem.
p.s. does anyone know how to reset the maintence required light on a 2001 type r? thanks

 

iv got a weird problem that im thinking is a vacuum leak now. i am hearind a hissing sound at the back of the intake manifold, sound exactly like a vacuum leak. however im getting good vacuum on by boost guage~18in/hg. now my idle screw is all the way in and yes, the more i turn it out the higher is gets...all the way to about 1500!!! so do you think i have a vacuum leak if right now that screw is all the way in and i still have a 800 idle??? its about 400 with the iacv unplugged. thanks

 

ttt. does anyone know?

 

If your base idle is set wrong, then the IACV will do what it can to compensate. That's why you can turn the idle screw a little ways without your idle changing.

But if it's not adjusted correctly, the IACV will be unable to stay within it's proper operating range when stuff (like AC & electrical loads) turns on & off.

"Base" idle is set by unplugging the IACV & adjusting a specific idle speed that's lower than your normal operating idle. Usually about 500 or 600 rpm depending on year & model.