LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

Has anyone installed a 52mm tb and not had it idle high?

Old Dec 14, 2003 | 09:26 PM
  #1  
Barry 94Formula's Avatar
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Has anyone installed a 52mm tb and not had it idle high?

I have 2 friends who have both installed 52TBs and they are having problems with them idling at about 1300-1500 rpms. One is a As&m and the other is a stock one bored out. If you installed one and it idled high how did you get it readjusted. Both cars are OBD2 BTW. They have tried adjusting the TPS and it still will not idle. Thanks
Old Dec 14, 2003 | 09:31 PM
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atljar's Avatar
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adjust the throttle stop screw. Use logger to read IAC counts and get them down. I keep mine about 15 at idle.
Old Dec 15, 2003 | 07:31 AM
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I am one of the two with problems. Mine is hanging up before it even hits the throttle stop screw and doesn't appear to be binding when off of car or even on car w/o running. Once I start it and drive it as soon as I clutch it, revs stay stuck higher 1200-1500 and you can kick the accelerator and it will kick down until next time you try to slow down. Very frusterating. I've even filed out the holes in TPS and moved it w/ no success but something is definitely holding it but can be pushed back down if you are under the hood. W/ key off and engine off it doesn't bind so I conclude it must be electrical(?) Come on guys, I know there must be more people on this board that run 52mm TB's. Please help. Thanks, Emile
P.S.-thanks for asking around Barry.
Old Dec 15, 2003 | 07:41 AM
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My 58mm BBK will idle at around 1300-1500 rpm's. Even if I adjust theidle screw all the way in, it will still idle the same....wierd...
Old Dec 15, 2003 | 08:59 AM
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Mine had the exact same problem it was idling at 1500 rpms and it wasn't hitting the set screw. If you run the screw in until it hits the tab and keep going the idle will go down. You have to have it run in some for it to work. I promise you this will work, it did for me.

Dan
Old Dec 15, 2003 | 11:27 AM
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Thank you Dan, I will try that and earlier I got off the phone with Tom Bishop who bored mine out located in TX and he said that too. I'll try it when I get home.
Old Dec 15, 2003 | 12:09 PM
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96 WS6's Avatar
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I went through this same exactly problem, the blades would hang up JUST before they were supposed to. If I went into the engine and pushed it back onto the stop screw it would work. There are a few ways to fix it, one is to wrap the spring around one more time. I can be quite difficult but it might work. Secondly, you can try lubricating all the joints/hinges to see if that helps. Clean all the crud (there should be a black ring of crud) where the blades touch the bores. I read that you already tried the TPS trick but it seems like you have a mechanical problem not electrical. If none of those work like what happened with my old TB, I contacted NOMAD from the board. He makes 52mm TB's and the one he sent me was pristine. Stock bored out with high polished blades, they look like mirrors =) No problems with it so far and it's been at least 1/2 a year.
Old Dec 15, 2003 | 12:31 PM
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Thanks WS6, already did the lubricating all points, It's a fresh throttle body that is newly bored so bores and butterflies are really spotless and tight clearances. I will try the stopbolt thing and IF that doesn't work might try the spring but don't know if it has enough room for one more wrap on the spring. It DOES stick RIGHT before it's supposed to so maybe this adjusting the stop screw might work as long as the IAT under it doesn't continue pulling in same amount of air that it already is(then it would just idle high all the time). 3 more hours and I'll give it a try.
Old Dec 15, 2003 | 12:50 PM
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what kind of skrew is the idle adjust skrew ??? a flathead a phillips ??? I have the high idle problem too , it seems like my blades shut all the way but theres only one way to be sure.
Old Dec 15, 2003 | 12:54 PM
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it is a torx screw, not sure on the size though.
Old Dec 15, 2003 | 01:21 PM
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I have teh BBK crap TB too. After spraying a little WD40 on the springs and drilling out the TB, I haven't had as many problems. The only time mine really sticks is in the winter when it gets really cold. It tends to idle too high.
Old Dec 15, 2003 | 02:12 PM
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Originally posted by DirtyDan
it is a torx screw, not sure on the size though.
egad how am I gonna get a torx bit into that lil hole , lol I hate torx !!!!!
Old Dec 15, 2003 | 02:25 PM
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Originally posted by BigJustinZ28
egad how am I gonna get a torx bit into that lil hole , lol I hate torx !!!!!
I bought a set like allen wrenches from autozone. They are "L" shaped so you can get it in there.
Old Dec 15, 2003 | 08:01 PM
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Originally posted by DirtyDan
Mine had the exact same problem it was idling at 1500 rpms and it wasn't hitting the set screw. If you run the screw in until it hits the tab and keep going the idle will go down. You have to have it run in some for it to work. I promise you this will work, it did for me.

Dan
YOU ARE THE MAN, DAN!!!! Thanks a TON!!!! I looked inside both the stock and the 52mm bored stock one(butterflies were actually all the way closed on the 52 but not the 48) and adjusted the stop screw to match how much light passed the butterflies on the stock 48mm TB and it's idling at 900rpms now, Yeah, boy!!!! You made my night. Setting the stop screw also got rid of the slight sticking closed the butterflies had. Thanks

Last edited by suprchrged400; Dec 15, 2003 at 08:05 PM.
Old Dec 16, 2003 | 03:54 AM
  #15  
96 WS6's Avatar
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Yea that's one thing I didn't mention. If you hold a light behind the TB you can see the points where it rubs and sand it down a tad bit. Or do as you said to fix it.

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