Whistling IAC

[CTX-SLPR]

Howdy,

I've finally got my Riviera through most of it's more fundamental issues and am now trying to tune it. It doesn't want to idle at the commanded rpm as well as I'd expect and after reving it up and holding it the IAC starts whistling and it continues whistling when it returns to idle.

I've adjusted the "minimum air" setting on the throttle blades with the TPS removed so I can get it to idle close to where I want it without the TPS acting like it's going off idle.
If I press on the IAC after it starts whistling the whistle stops and the idle doesn't degrade. I pulled it out and greased the O-ring with dielectric grease (decided it was better than PTFE or white lithium) and cleaned the pindle and seat, but that didn't really change things.

I have a spare IAC that I'm thinking of throwing on, thoughts?

Thanks,

[TheSilverBuick]

Is it a vacuum leak whistle? Mine only whistles if I back off the idle screw and close off the throttle blades completely. It kind of whistles at high idle when cold but stops completely the moment I give it throttle.

[CTX-SLPR]

I thought it was a leak but the dielectric grease should have plugged that I would think. I guess it might be leaking internally.

The whistle is constant after I run it up to 3000rpm or so for anything more than just a quick rap on the throttle.

[TheSilverBuick]

Di-electric grease won't plug a vacuum leak, nor will any kind of actual grease. It'd just get pulled into the intake...

[Barry Donovan]

all aluminum and aired for a long time? a lot of things will have to whistle until nitrogen/vacuum calms the fresh will to oxide. You should hear my little subaru at 22 inches, intake freshly mounted...several days. Whistles everywhere

[CTX-SLPR]

Di-electric grease won't plug a vacuum leak, nor will any kind of actual grease. It'd just get pulled into the intake...

Not my experience for small leaks around O-rings and the like. Now a real leak in a diaphragm or broken nipple I can agree with you.

I'll pull the spare off of the TB and see how it's O-ring is before I swap the IACs to see if it goes away with that.

[SpiderGearsMan]

ground the aldl to run the IAc all the way in ...I have a thexton tool for that too

[BigAL]

If you are opening the throttle blades where the TPS is reading that it's coming off idle you need to drill a hole in the throttle blade to allow more air through, so you can keep the TPS readings in range for when at idle. Also you'll need to adjust the throttle blades so the car idles close to your commanded idle, that way the IAC doesn't have to compensate to much to keep the idle at the commanded valve.

[CTX-SLPR]

ground the aldl to run the IAc all the way in ...I have a thexton tool for that too

This car is OBDII, I've not done enough digging to see if I have command for that in my scanner but I'll definitely try it.

If you are opening the throttle blades where the TPS is reading that it's coming off idle you need to drill a hole in the throttle blade to allow more air through, so you can keep the TPS readings in range for when at idle. Also you'll need to adjust the throttle blades so the car idles close to your commanded idle, that way the IAC doesn't have to compensate to much to keep the idle at the commanded valve.

I pulled the TPS off of the TB when I was adjusting the idle so best I can tell it's not registering TPS delta when I'm adjusting it. I'll put the other IAC on tonight and adjust the idle with the "min air" to get it close to my target and see if the IAC can do it's job more in mid travel range vs. full open that I think it is now.

[BigAL]

This car is OBDII, I've not done enough digging to see if I have command for that in my scanner but I'll definitely try it.

I pulled the TPS off of the TB when I was adjusting the idle so best I can tell it's not registering TPS delta when I'm adjusting it. I'll put the other IAC on tonight and adjust the idle with the "min air" to get it close to my target and see if the IAC can do it's job more in mid travel range vs. full open that I think it is now.

Just to clarify, when adjusting the throttle blades to set base idle you need to disconnect the IAC. And by disconnecting the TPS I assume you mean you disconnected it from the throttle body, but left it plugged in. Still after adjusting base idle if the throttle is open to far the TPS is still going to read that it is off idle once you put it back on. IMO you should leave the TPS connected to the throttle body, disconnect the IAC and set base idle and drill a hole in the throttle blade if your opening the throttle blades to far. I just got done doing this on my '99 Z28, after the tune I got when first starting it up it would hunt for an idle, when I disconnected the IAC the idle shot up to 1500rpm I have it commanded to idle at 950rpm, so the IAC was working real hard at restricting the amount of air coming into the motor to idle it down. I adjusted the idle to about 1050rpm with the IAC disconnected and now it doesn't hunt for the idle anymore. By the way disconnect the IAC with the car turned off, then start it and adjust the idle.

[CTX-SLPR]

The TPS on an LC2 is adjustable so I took it off and left it plugged in and then adjusted the idle to something better with the IAC still working then put the TPS back on with it at the far end of adjustment. With my scan tool tomorrow I'll first see if I can 0 it, then see if I can log it's position, and above all set the TPS to 0 when the throttle is full shut.

[SpiderGearsMan]

similar to this caddy tool

[CTX-SLPR]

Other IAC still whistles...

Didn't have enough time mess with the computer but it seems like I have a vacuum leak somewhere. Will try to track that down and then get back to trying to fix this.

[BKBridges]

Is it a vacuum leak whistle? Mine only whistles if I back off the idle screw and close off the throttle blades completely. It kind of whistles at high idle when cold but stops completely the moment I give it throttle.

Si,
Once you are off idle the IAC is usually driven open and occasionally moved about (OBDII ,mfg needs, etc) but for the most part it shouldn't make noise at full count unless your throttle body IAC ports are really restricted (bugs?) Id look for that vacuum leak.

[CTX-SLPR]

SOLVED!

It was a problem with the gasket between the IAC housing and the throttlebody. The original gasket for the TB had 2 holes for index pins that the new housing for the later model IAC didn't use plus the new IAC housing had rectangular holes vs the oval in the TB. All combined the holes were barely uncovered and as the IAC retracted at normal run it whistled through the holes in the gasket.