Just swapped on a holley 52mm TB. It idles perfect in idle with the brake on (700rpms), but in park it idles at 1500. It might be the gasket on the bottom of the TB? The blades arent catching and the idle adjustment screw didnt really do much.

 

my buddy is goin through the exact same thing. (but he has 58MM holley). his IAC readings are down to zero. which means either his IAC valve is bad, or he has a vacuum leak. if you suspect the tbody gasket, use some parts cleaner spray w/the small straw and spray it on the gasket all the way around slowly. if the idle speed lowers, youve found the leak. you can use this tactic all over the eng. to find potential vacuum leaks, but be careful since the cleaner is extremely flamable! if you have a sp. plug wire arcing, you will ignite the cleaner. thats why you dont continuosly spray the cleaner. short bursts w/a couple sec.s time inbetween works best. if you dont find a leak, check into the IAC valve. also, i havent seen it yet, but there is supposed to be a mod that involves fixing the IA air passage ways to help these Tbodys idle better. if someone has a link, list it here please.

good luck
chris

 

A lot of aftermarket throttle bodies need modification to the IAC to work properly. I had to to exstensive modification to mine to get it to idle right. I put on a BBK 58mm. I did something similar to this link.


http://jrevans.fbody.com/car/TB_mod/

 

I think my problem is the lack of the bottom TB gasket. I was not thinking and totally forgot to put a gasket on the bottom. I couldnt reuse my old one cause it was disintegrated. Gonna pick one up tomorrow, but they want 30 bucks for it!!

 

you should check around for better pricing....thats ridiculous

 

The gasket for the IAC housing and clean air cover are sold under part no. 17113074. I purchased this very set last week for $12.00. I think what the dealer may be trying to sell you is a complete TB gasket set, which will inlcude a number of things you don't need from your description. The last time I bought the complete set it sold for $38.00.

 

Yea it was a whole set, but it was all that the local place (pep boys) had in stock. I am gonna hit the dealer up tomorrow. Thanks for the part number.

 

i cant get the idle to come down from 1100 on my 58mm tb.

Its almost like the blades are too big for the bore in the throttle body and i cant get it to come down all the way.

i turn the screw out so that the TB will close more.. yet all that happens is the screw moves but the TB blades dont.. like there hung up in the bore..

hmmm any ideas?

 

Can you push them shut? Are they hung up on something like bad machining? Did you drill a very large IAC port?