hello have a 1990 gta 5.7 crate engine aftermarket runners intake and a holley 58 mm troddle body baffles will not pull closed , when u let off gas pedal normally it will hang open enough to keep rpms @ 1200 if u tap pedal it will drop to 850 . nothing is binding . only does this while engine is running .if u turn engine off u can watch it close as vacuum drops. how do i relieve this vacuum open issue?????? dandav65

I had a Holley 58mm. Truthfully i hated it, it did the same thing. I got a shaft and butterfly rebuild kit from Holley and then sold it on ebay. I bought a BBK and it works great. The difference is brass butterflies on the BBK vs. aluminum on the Holley. If the shaft has any play in it, (from side to side) it will bind. I tried an extra spring and that didn't work. If you can find even a stock throttle body to try, just to make sure that's what it is. With play in the shaft, you also are getting a vacuum leak.

it only does it under vacuum , have checked 4 vac. leaks with carb spray 4times removed it took it apart etc did brass rod work 4 u?. did u have it on a stock phenumn ,and did u have to drill a passage for iac air by pass on yours? just wondering holley tech guy never heard of this problem B.S. ???? was going to try spring .I willl look for another trodddle body. thanks 4 input

I had it on a ported plenum. I did not have to drill holes for anything. All it takes is a couple of thousands of side play in the butterfly shaft to make it sticky when the engine is running. The rebuild kit i got from holley seemed to tighten it up, but the kit was pricey and after i rebuilt it, i just didn't want it anymore so i sold it.

ok thanks for reply , holley trd body a disapointment .thanks

I have a holley 52mm brand new thats doing the exact same thing.

It will hang the throttle blades open just a tiny bit when the engine is on.

I noticed if I undid the screws on the throttle plates just a tiny bit it fixed it but I was always scared the screws would come out later on and suck the plate and everything into the engine.

I think they might be pressed at the back so they wont come the full way out.

I live in another country and drive my car when I come back for hollidays, ran out of time to play with it last time.

I would be careful backing out the plate screws, maybe if you use a loctite product to keep them from loosening out, but they do come out so you can replace them. Its too bad Holley wouldn't make a "red brass" throttle plate to replace the aluminum.

I actually tried to remove the screws in order to loctite them and found I could not unscrew them fully as they seemed to have been pressed or something at the ends to prevent them from undoing the whole way.

I will be back home with the car in 2 weeks so I will have another try then.

Its a shame cause half turn and the problem goes away.

It sounds like there's slop in the shaft that the throttle blades rotate on. I had a similar issue with the TPIS throttle body that I had on my Corvette. With the car off it worked fine, but when running, it wouldn't fully seat because it would bind slightly with the air pressure on it. I used to be able to temporarily fix the problem by oiling the shaft, but that only lasted for a couple days.

Fortunately, I've had no such problems with my Holley 52mm throttle body.