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rang-a-stang
07-29-2019, 07:39 PM
The 454 TBI that sits on my AMC 401 whistles when the air filter is open. It's pretty obnoxious. Is that normal?
stew86MCSS396
07-30-2019, 12:18 PM
Nope. Less air passing through iac and more through throttle blades should quiet it down. Also make sure your adapter for the 454 tbi has big enough footprint to cover passages at base of the otherwise you'll get a vacuum leak that may sound like a whistle.
rang-a-stang
07-30-2019, 09:53 PM
That makes sense. I'll take a look at my IAC motor counts when at idle and see if I can adjust the throttle screw a tiny bit and what difference that makes.

Yep, my adapter was verified when I installed it.

Thanks!
1project2many
08-01-2019, 03:13 PM
The 454 TBI that sits on my AMC 401 whistles when the air filter is open.
I'm not really clear about what this means but if it's happening while driving you could try adjusting the throttle follower and if it happens at idle you may find decreasing spark advance one or two degrees is enough to help.
tayto
08-01-2019, 04:04 PM
my BB tbi did the same thing. i had to bring IAC counts up in the 25 to 35 range, instead of the ideal 5-15 range.
rang-a-stang
08-02-2019, 02:41 AM
I'm not really clear about what this means...
HAHA! I make it sound like a I am driving around without an air filter.

What I mean is, when I am idling my TB whistles. If I open the air filter lid, it is pretty loud. If I put the lid back on, it's only noticeable.
1project2many
08-02-2019, 05:43 PM
HAHA! I make it sound like a I am driving around without an air filter.

What I mean is, when I am idling my TB whistles. If I open the air filter lid, it is pretty loud. If I put the lid back on, it's only noticeable.

Yes. It did look like you were pulling the air filter for that "big engine" sound. Some good tips have been offered. Check base throttle angle, check idle speed and adjust slightly if necessary, check and retard ignition timing slightly. You should be able to take care of this fairly quickly.
rang-a-stang
10-10-2019, 02:17 AM
Finally have my truck running again after some other drama.

When I tune my IAC, what should I be looking for? When I am idling, IAC counts are typically between 8 and 16 with most of the idle time set at 12. Is that normal? It idles very well and I don't want to mess that up just because it is annoying when I open my air filter...