So here's the plan ....

[Bob Holmes]

I'm not suggesting that he not do an IAC, I'm just saying its not number 1 or 2 or 3 ... on the list of things to sort out.

Just saying don't get stuck on a tertiary issue, make it run.

[Bamfster]

So what's this pot-o-string he speaks of?

[Bob Holmes]

Takes this, drill a hole in the arm, then mount it so that when you cable it to your linkage it pulls on the arm.

Came in a variety of GM products in the late 80s, early 90s.

[BKBridges]

Or something like this can make the TPS do its thing
might want to clean up your carb body a bit better than me though...
Bruce

[TheSilverBuick]

[ATTACH=CONFIG]6062[/ATTACH]

Takes this, drill a hole in the arm, then mount it so that when you cable it to your linkage it pulls on the arm.

Came in a variety of GM products in the late 80s, early 90s.

That's the style that's on my Holley 2bbl TBI that's on the T-bird.

[Bamfster]

[ATTACH=CONFIG]6062[/ATTACH]

Takes this, drill a hole in the arm, then mount it so that when you cable it to your linkage it pulls on the arm.

Came in a variety of GM products in the late 80s, early 90s.

Ok .... I see said the blind man. I like the simplicity of that ... hmmm

any idea of specific app? it makes it easier to look up on rockauto ....

[CTX-SLPR]

Ok .... I see said the blind man. I like the simplicity of that ... hmmm

any idea of specific app? it makes it easier to look up on rockauto ....

That looks like the one that's on my 86 Turbo6 TB. Try seeing if a truck cross refferences off of rock auto.

[Bamfster]

[ATTACH=CONFIG]6062[/ATTACH]

Takes this, drill a hole in the arm, then mount it so that when you cable it to your linkage it pulls on the arm.

Came in a variety of GM products in the late 80s, early 90s.

Found it! ..... app is '90 chevy truck w/350.

[Bamfster]

And thinking ahead ..... as far as I can tell, are there any reasons that the IAC cannot be made/built into the intake manifold? I understand that it needs to connect above the throttle plates ....

I'm using the size/diameter of the IAC valve as a guideline for the size of the IAC channel, or is this one of those things that can't be sized to big (within reason) as it's the distance the valve moving off it's seat that determines the amount of air that flows?

[Stich496]

instead of a iac.. could you just use a a/c idle pliunger, that they used to up the idle when a/c was on..
I'd think you could set that to hold the blades open just enough to idle at whatever rpm your want..

[TheSilverBuick]

Sure it can be built into the intake. You can look at examples on the DIYautotune page of metal blocks that have a few holes drilled in them that the IAC bolts too, then you connect large vacuum hoses (3/8th?) to it, one goes into the intake and the other end into the air filter housing (to pull filtered air). Then the IAC block can be mounted anywhere, including the firewall. Just drill and tap either a spacer or the intake for a 3/8ths (or size of your choosing) port.

The A/C plunger isn't a bad idea, though I don't think any one I've tried has acutually worked.

[Bamfster]

And just thinking about what we've talked about Randal, wouldn't the A/C plunger still need to be messed with periodically when changing altitudes?

[TheSilverBuick]

The issue I've had is that with the standard MegaSquirt code, the IAC opening amount is tied to temperature. So when cold you have it opened more for high idle, and it closes as the engine warms up (which as it closes you have to match the warm up enrichment settings so you don't make it too rich). It works very well and consistently that way too, as soon as it hits ~160*F I had it at normal operating rpm, and made it bump up the rpm if it got over 200*F (for waterpump and fan flow). The problem I've ran into to is it behaves very much like a carburetor in respect to idle settings. When I go down in elevation and the air get's denser the idle rpm goes up even though the IAC is open the exact same amount as normal. Then if I lower the idle rpm (via the IAC settings, screw breaking out the screw driver ) while I'm at low elevation, the car will stall when I get back to Ely because the idle rpm is too low. All my carb'd cars have this problem, and this one did too prior to the EFI conversion. I get a 400rpm increase in idle speed from here to Fontana, CA. Pretty annoying going from 800-900rpm to 1200+rpm.

Now with the MS2/extra code there is an rpm targeting feature. I haven't been able to get it to function the way I want to yet though. It targets the rpm just fine, only it takes it about a minute to target it. Compounding the problem is the fact it doesn't seem to take much for the IAC to reset itself, so the IAC will regularly open all the way up or close up all the way (depending on settings), causing either the idle to be at 1500+rpm and sloooowly come down, or to be shut and the car barely run at a stop and if it doesn't stall the idle will slooowly start creeping up to the target number. I haven't played with it enough yet to know how to get around this. The good news is, worse case scenerio I turn off the idle speed targetting and go back to the temperature controlled setting.

[Stich496]

And just thinking about what we've talked about Randal, wouldn't the A/C plunger still need to be messed with periodically when changing altitudes?

not if you used the punger "on" at the low dense air and the off when you have the high dense air and use the screw setting as the throttle stop so it can't fully close

[Bamfster]

And to be honest Mark, I've never messed with either to know if that'd work or not. I had a 1980gmc truck that had the AC plunger. It seemed to function right and I never messed with it. It might be worth researching tho...