2.0L Idle Adjusting Question

[MazdaSpeeder]

So I've done my reading here and in the shop manual, and it appears that if one adjusts the AAC screw on top of the throttle body (not the hex screw further out) it will raise or lower the idle. Some people claim the PCM will eventually reset the idle, but no one has actually had it happen, so I decided I would try it for myself because with my front insert installed my RPMs match the resonant frequency of almost everything in my car. I discovered that 2 1/2 turns counterclockwise will raise the RPMS about 150, which is all I want. Here's my question:

When I raise the RPMs, I noticed a much more pronounced whistle/hiss coming from my driver's side in the engine compartment, near the wheel. It sounds like this is coming from the cone air filter, and it's loud enough to be noticeable standing next to the car at idle. When I reduce the RPMs back down, it is still there, but less pronounced. Anyone have any ideas what this is, if I can quiet it down (I have a Simota CAI & filter) or if it's just an inevitable byproduct of raised RPMs?

 

[MazdaSpeeder]

bump (lol2)

 

[njaremka]

i'm going to guess that the hissing is a byproduct of the increased idle speed and the CAI

 

[MazdaSpeeder]

Yeah, I think that may be the case...I'm wondering if adding a better filter (K&N) might help alleviate some of that...

 

[njaremka]

is it really that much louder?

 

[FunkRider]

In the past I've put a dent in a cone airfilter to change the way air flows through it to stop whistling. Doesn't always work though.

 

[P-Funk!]

Just more air moving through it. Ignore it.

 

[MazdaSpeeder]

In the past I've put a dent in a cone airfilter to change the way air flows through it to stop whistling. Doesn't always work though.

I pulled off my filter (the cheap one that came with my Simota Twin Charger) and it had a hole in it! I replaced it with another cheap filter (I'll get around to a K&N one of these days) and thought that would surely solve the problem, but when I fired her up, I hear the same noise. At first I was going to leave it alone, but it's really starting to piss me off. It's loud enough that standing next to the car, the noise is audible over the relatively quiet engine and when rolling around 2-3K rpms, I can hear it in the cabin. The only thing I have done recently is change the PCV valve, and how that would affect it, I have no idea. It's definitely coming from the CAI...I'm going to keep looking, but I welcome more suggestions.

 

[StealthWyvern]

I pulled off my filter (the cheap one that came with my Simota Twin Charger) and it had a hole in it! I replaced it with another cheap filter (I'll get around to a K&N one of these days) and thought that would surely solve the problem, but when I fired her up, I hear the same noise. At first I was going to leave it alone, but it's really starting to piss me off. It's loud enough that standing next to the car, the noise is audible over the relatively quiet engine and when rolling around 2-3K rpms, I can hear it in the cabin. The only thing I have done recently is change the PCV valve, and how that would affect it, I have no idea. It's definitely coming from the CAI...I'm going to keep looking, but I welcome more suggestions.

It's the intake man mine does the same thing...

Edit: Also my stupid simota filter has a small hole it in to!!!

 

[MazdaSpeeder]

Edit: Also my stupid simota filter has a small hole it in to!!!

What's up with that?!? I'll post a pic later but I have NO IDEA how it go there!

 

[P-Funk!]

Is the filter touching something else (bracket/hose/hard surface) and the engine vibration is chaffing a hole in it? Especially if the hole is in the same place...

 

[jamesk]

thats the noise high flow filters make. i do not think you can really do anything about it. it is deff. somthing not to worry about

 

[BackRoadGTO]

Bringing this one back from the dead. I just put on an aftermarket intake and had the same loud hiss OP was talking about. It comes from the idle adjust screw he was talking about on the throttle body (the philips head one on top). Mine was pretty far out so I ran it back in until the hissing stopped, which dropped the idle so low the engine wanted to stall. I pulled off the battery cable to reset the ecu and now its relearning the idle point just like any other ECU reset. My idle is still rough (I've done all the other common rough idle fixes and was hoping one of the cracks in the OEM intake tube was leaking) but there is zero sound of hissing now. I don't know if the car picked up any power, but she sure sounds like she is trying harder lol.

 

[eszoom]

thanks for bringing this back. i have the same problem. changed the intake manifold and the idle was eratic. so my son raised the idle. it has settled and he dropped it once and i told him he can drop it again. i have the whistle or hiss and it's pretty loud. good to know i wasn't the only one. it runs good but just has the hiss. thanks again, backroad.