How does one adjust idle on the LT1 throttle body?

[evilmiata]

Just like it says. There is a hole between the twin butterfly flaps, but there doesn't seem to be anyway to close it. Should I just jam a screw in there?

[RacerX11]

RE: How does one adjust idle on the LT1 throttle body?

Are you using the IAC? IIRC, the hole in the throttle body leads into the passage for the IAC, which meters the air to the engine. Do you have any pictures of it installed?

Marty

[evilmiata]

I'm not using the IAC. I took it off the throttle body and cut a piece of 1/16" steel to cover the gaps. Besides, the motor is idling at 2000 rpm. From what I understand, the IAC is closed at startup, anyway.

[RacerX11]

The IAC opens to a pre-determined position at startup to create the proper flare-up rpm. Can you see where the air is bypassing the throttle? Is it past the plates, or is there a passage that is open? Do you have any vacuum leaks? Do you have any pictures?

If you have the room to add back the IAC housing, it wouldn't be very hard to make an adjustable bleed valve that replaces the IAC, and allows you to manually adjust the idle speed without moving the throttle plates, and having to re-adjust your TPS range.


Marty

[evilmiata]

Unfortunately, there is a ~1/8" hole between the butterflies. This hole completely bypasses the idle air control. Considering this hole was designed with a 5.7l motor in mind, its not suprising that its spinning a 3.4l much higher. I don't have any pics (the car is 1 hour away), but I'll take some when I'm back down there.

[TurboZ24]

I have no issues using the dual throttle on mine, but then again, I simply adjust the throttle plates, then go too the laptop and go "recalibrate TPS" and reset it.

Adjusting the throttle plates on a stock ECM will result in an incurrent reading on the TPS sensor, causing the ECM too think that you are not at idle.

Mine will idle as low as 600-700 rpm with the hole still there, but I have too adjust throttle plate stop.

[bszopi]

AFAIK, evilmiata is running a Haltech, just like you Curtis, so it should be just as simple for him...

[TurboZ24]

It should work fine then, unless mine uses that much more air at idle. People have mentioned that it's spewing way more exhaust just at idle than a stock 3.1, though......

I shall in detail explain Haltech throttle calibration then...

Disconnect and remove the IAC. Pull out the pindle as far as it can go, reinstall the IAC, but do not hook it up. Then, start the car and adjust the throttle plate until you achieve a couple hundred rpm less than you want too idle the car at. Recalbirate the throttle position sensor, then reconnect the IAC.

On most Haltechs, the IAC is really only intended too control the idle up features.

Also, which Haltech model do you have? E6GM? E6A? E6K? E6S? E6GMX?

Man, I need too go get his car and just drop my motor in there. I've been looking for an excuse too dump FWD......

[bszopi]

And he's not using the IAC (as stated above). I would think it could still work the way you are describing it. By extending the pintle all the way out, you are effectively blocking off the IAC passage, and it sounds like that's what he did.

Of course, I'm just going by what I'm reading and could be totally off...

[TurboZ24]

Ok, did a little digging on his website, and I assume he is using the Haltech E6K that was in the car before....

Ok, there is an issue with the E6K and the 60 degree... I believe it goes back too the timing control, I was messing with a friend's Beretta 3.1 trying too get the E6K hooked up and it would idle at 2000 no matter what I did with the TPS. The only way I could lower it was too screw with the ignition control settings.

[evilmiata]

Wow, you guys are on top of this stuff! My plan is to lower the throttle plate bumpstop and try to fill in that hole. I am running the E6K and removed the IAC.

[evilmiata]

Alright, there is tons of air coming through that tiny hole between the butterflies. I used a 10x24 screw to fill it in and remounted the throttle body. Not only did it no longer idle @ 2000rpm, but it couldn't even start. Therefore, I removed the bumpstop and installed it so it can be adjusted from the front of the throttle body. I started with the bumpstop screwed all the way in and backed it out until I could idle correctly.

[bszopi]

So is it fixed then?

[evilmiata]

I consider it fixed. The best I could do with modding the TB was 2000rpm. Now I've got it at 700rpm running rich for cold starts. Once it starts up, I can lean out the mixture and have a nice idle @ 800rpm. Haltech has a programming section for cold starts, but I haven't gotten that far.