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LSX454 swapped 95 BASS burb.

Little lower, little cooler, bigger sounds.
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I'd also confirm you IAC valve is doing what it think's it is, I've seen bad IAC valves, and also, there are Chrysler and GM IAC, and if it got mistakenly replaced they look the same, plug in the same, but have 2 pins that are swapped. That can cause the IAC to plug in, and not work. I think its the A & C pins if I remember correctly.
 
I bought the TB from Amazon for an LS. And the iac came with. So it's probably bottom barrel cheap.
I do still have the original from the engine, but it was old as hell and crusty looking.
 
I like the real Amazon, the jungle of South America. The big tech company, not so much.

I would definitely verify your IAC is working. You should be able to change the parked position from 0 to 100 with the key on and the engine off and watch it close and open. I've lost count of how many times I have seen that issue.
 
I know it works to some degree. It's what's causing my start up ramp. I watched it come on, ramp to 50 and come back to 0.
 
Yeah, that's a good indication of the RPM follows the IAC % closely.

Just double check it, and then look for a vacuum leak.
 
Back of my TB looks to be ok. This is the pic from my order.
I'm going to plug my pcv hose at the intake first, see what happens, then see what I can find if that's not it. I keep thinking maybe it is, because It bothered me when I was doing it that the way the stock engine was HAD to be a massive leak. Did a whole bunch of Google searches on pcv diagrams and all kinds of texts back and forth with beags lol.
 
I think we have the same throttle body, mine sounds like a vacuum cleaner at idle but as soon as it goes off idle it goes away. Never heard of that before.
 
I don't trust the pic, because that is one of those dual 4 and 3 bolt throttle bodies. And sometimes that doesn't work with the factory seal alone and you may need a plate between them. You have to take it off and look and the contact pattern to be sure.
 
Maybe its not a dual bolt pattern, I'd still check it, take a look at this professional installation they recommend...

I've seen people mount them backwards in race cars with an ice intercooler in the cab, but never with the valley plate on wrong too....

Although I guess when the heads are just sitting on there with no cam or crankshaft it doesn't really matter.


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I think I just have a low quality TB lol.

No leak to be found anywhere.
Took the intake tube off, and with the screw all the way out the butterfly was cracked slightly.
Pushed it closed with a screw driver and felt something give. Idle came down, iac at 9-11.
Gassed it a bunch came back to that every time. Idle around 715-730.

Until I hooked up the pcv again. Iac went to O-1%, and idle came up to around 750-780.
 
Good find, you'll need to recalibrate the TPS after that.
 
On a side note I did figure out the starting issue where it ramped to 1800 and held there. It was the IAC starting position, hold time, and decay rate. Much better there now.
Reset the TPS, and even with the pcv hooked up it idles with the IAC between 1-9.
 
TB when new, screw all the way out.

Screenshot_20220706-203815.png

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Set parked position at 30% also.

The parked position and starting seem to get confused on the forums. All of them I skimmed.
Starting seems to have nothing to do with parked position. Parked position seems to be where it stops at when your off idle and accelerating.
When I start it it goes to the hold position (different setting), and then decays down.

Which is higher than the set parked position.
But after it's running, and I'm increasing the throttle the IAC is opening too. But it stops at 30% (where I have the parked position set) and won't open any farther than that.

Why it opens at all when the butterfly is open is beyond me
 
shady said:
Set parked position at 30% also.

The parked position and starting seem to get confused on the forums. All of them I skimmed.
Starting seems to have nothing to do with parked position. Parked position seems to be where it stops at when your off idle and accelerating.
When I start it it goes to the hold position (different setting), and then decays down.

Which is higher than the set parked position.
But after it's running, and I'm increasing the throttle the IAC is opening too. But it stops at 30% (where I have the parked position set) and won't open any farther than that.

Why it opens at all when the butterfly is open is beyond me
Click to expand...

It has to open when the butterfly opens, otherwise it would die when you let off the throttle. It has to have a cushion of airflow so it can "catch" the engine on the way back down and bring it down without stalling.

And base on what Holley says, your other forums are backwards. This is directly from "Holley"...

1657197369622.png

You can also adjust the Startup IAC Hold Time and Decay time seperately.

What you are referring too is the IAC Ramp Down which has its own hold position, decay time, and RPM to start and renable.

1657197521703.png
 
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FYI, don't bother searching the net for these things first, because you will get many wrong answers as you are finding out. If you want to know what something does, just click on "Help?" in the top menu and the Holley software will tell you what it does without sorting through all the BS online.

You can also look at the entire manual by clicking on the Help drop down. The "Help?" takes you straight to the section you are currently in.

It makes no sense that it would go to "parked" when you are driving and then go to "hold" when you are parked. But that's whey they are saying out there I guess.
 
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I was basing it on what I found. The park position I set had nothing to do with start up or cranking.
When starting or cranking it follows the hold position, not the parked setting. It'll shoot past that parked setting easily on start up.

The net was saying exactly what that Holley thing said. But that is not how it is working lol.
The only time I get that 30% is after it's started, in gear, and I'm accelerating. At that point it stops when it hits 30 and doesn't open any farther.
And curiously, after setting that parked position lower, it feels more spunky driving through town. Exactly where it was lacking.
 
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