I was reading a Ray T. Bohacz article from 2005 and it mentioned a later, second-generation design IAC that GM started using on some applications in the early '90s such as the later 3100. The new design is reported to be faster and more responsive. Due to wear and age my car could use a faster one than stock. I have two stock IACs (one almost new) and they both work as they should from the factory. I did some Googling and found P/N 17111809. It is not a direct bolt-on, but I was wondering if anyone here has used this in a TPI application. Here's a pic: https://www.summitracing.com/search/...fault&N=%3A%2B

Principle of operation is the same so you just need a pinout and a way to mount it. Though I can't really see it being all that much use. What problem are you trying to solve with this wildly inefficient repair/modification?

GD

I'm just not interested in changing my lower plenum-to-head gaskets right now. The only issue it is causing is an unintended idle blip that returns to normal idle after about 5-10 seconds on clutch-in decel situations. I've already switched to a manual tune that has all necessary changes that affect idle quality. The throttle is not sticking and is always at 0.51-0.55V when it should be according to datalogging/display. The behavior is also intermittent. It's not using coolant or doing any of the other things that are unpleasant about a very slight leak. All vacuum lines are fresh as are the rest of the intake gaskets. A more responsive IAC motor is worth testing at a sub $50 price point.

If you have the capability to fab that IAC into the throttle body quicker than changing some lower intake gaskets my hat's off to you friend. Go for it.

GD

Well, that's one thing I was concerned with along with the signal and the pintle travel. I was considering just threading the barrel.

With enough TIG welding and machining I'm absolutely positive I could bribe a friend of mine with booze to git'r done but I wouldn't call in a favor of that magnitude for a mod I believe will accomplish nothing.

GD

Can you explain this in more detail rather than acting like the sun won't rise tomorrow if i don't spend 12 hours changing the intake gaskets? That's how much time projects like that take me. I have a ton of free time at work to do things like make electrical connectors but I'm really sick of the car being torn apart for months at a time. My garage time is very limited. For example, one time I went on a surprise date and it pushed back me porting the plenum by three months. I can understand why changing the IAC may not benefit me but responses like this are why I ask most of my questions on FRAAX instead of here.

Take a look at pics of the two parts. One is threaded, and one has mounting ears. Also there's the not-insignificant problem of ensuring that the number of steps from fully open to fully closed is maintained to a high degree of accuracy meaning the IAC needs to be located within a few thousandths of an inch (I would estimate within about 0,010"). This would require adding a significant amount of material for the mounting ears, then accurately machining it on a mill so that the new IAC would be mounted correctly and located accurately. That's all assuming there's even room to mount it - which is not a foregone conclusion as I haven't actually measured to determine if it's even possible. It very well may be - but won't be worth the time it would take and as with a lot of things in this hobby - if you have to ask how to do it - it is very possibly the case that you aren't equipped or can't afford to do it.

By comparison some lower intake gaskets are childs play and could be done in an afternoon.

GD

Now that's more like it! Thank you.

I used a LT1 throttle body. Uses a different IAC housing with the newer IAC. Only used it because it matched the Vortec PCM I was running the TPI with at the time.

That being said I am sure your sluggish return to idle is in the ECM programming. Its throttle follower designed to allow the engine to settle to idle at a slower rate, preventing a spike in hydrocarbon emissions when the throttle is slammed shut.

Hmmm, makes sense. And it didn't do it until I swapped to a manual since it had drag from the torque converter and pump perhaps. Or maybe I simply wasn't noticing it as much with the automatic. Maybe both.

Oh, and that's why my truck (stock tune, drive-by-wire) overfuels/throttle hangs when I chop the throttle, huh?

After making two small changes to MAF Table #1 to richen the mix at cruise (.73V, .91V) then datalogging again (paying special attention to IAC steps in response to throttle voltage), I have determined that the stock IAC is plenty responsive and a swap would likely not be beneficial, especially due to the amount of work involved as pointed out by the forum. I have also determined that the possible air leak due to old head-to-lower-plenum gaskets is not worth bothering with after more study in both datalogs and road-test feel. Also after learning from the forum that the computer was going to lag the idle anyway despite the input from the IAC being spot on. I have tried many settings to the .55V fueling and have settled for slightly high BLMs (134-137 for very short periods of time that return to 124-132 fairly quickly) to keep the idle from getting too high. Maybe one of these days the intake will have to come off but today isn't the day. Probably the day I buy some heads and port the lower plenum.

Thanks to all for your input.