Idle problems after TB install

[Dopey]

Hi All,
I installed a new 80mm throttle body + bored out LS6 intake manifold about a month ago, since then I am having problems with rolling idle..... If I sit at the lights after 5 seconds the idle drops to 1050rpm (desired = 800), but as soon as I start rolling the idle goes to 1800rpm.....

I know its not a vacuum leak as Ive tripple checked and it also is fine if I am stationary for long enough....

I am running COS3.... any ideas?

One thing I did notice is that the butterfly has a hole drilled out, but it looks like the drill bit did not make it all the way through (looks like a realy bad countersink).... Any thoughts?

I dont had a look at the throttle cracker/follower details in the idle section, but I dont really understand what it is they do exactly......

[dfe1]

Part of the problem is that you've installed a larger diameter throttle body and didn't tell the PCM. It's computing the amount of throttle opening needed based on the assumption you have a stock throttle body. There are a number of ways to solve the problem, but the best approach is dependent on other modifications, the degree to which the tun file has been reworked and type of throttle body (cable or wire).

[Dopey]

Sorry forgot to mention, im running COS3 in OL....

I was uner the impression that being that it is a map tune it would just hit a higher MAP value at a lower throttle opening... which would just mean it would be looking at another table....

The car has a full exhaust sytem (extractors, cats and catback), OTRAI, bored out manifold neck and 80mm TB.

I have run the AUTOVE a few times to make sure that the afr's were still good, TB only seemed to effect the WOT are of the VE table.

[TAQuickness]

On the off chance, have you zero'd your TPS sensor? I recent changed manifold and TB setups (90/90 to LS6/78mm PTB) and did not have to make any adjustments to the tune.

[redhardsupra]

http://www.marcintology.com/tuning/TBresizing.xls use this

[Dopey]

http://www.marcintology.com/tuning/TBresizing.xls use this

Sorry mate, any more info on what to do with the spreadsheet? Appreciate the input, makes me feel like im in way over my head! haha, here I thought that all i'd need to do is the AUTOVE....

[vxchev8]

............. here I thought that all i'd need to do is the AUTOVE....

What yours didn't come with a button that you push that will automatically tune your vehicle :grin: send it back :laugh:

Anyway back to the topic

Does the t/body have the same rectangle hole ( per pic) as your new one. If not mill it out to the same size as you stock throttle body. It will stop the high rev's when you stop the car. The hole in the butterfly should be the same as stock. Common problem with SS induction and the GTS throttle body as they were designed for a pre VT IAC which had a different pintle design.
The pic is a Starr t/body that was made correctly.

Discussed here (http://www.ls1-australia.com/forum/viewtopic.php?f=64&t=446&start=0&st=0&sk=t&sd=a&hilit=hole+throttle+body)

http://www.jhp.com.au/img/products/extra/84mm-h.jpg