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About 6 mounts back I got a TPIS 58 MM Throttle body off the forum looked new did all the work to install it on my 93 LT-1 auto ( lots of work ) it will not ideal any lower that 1500 RPM . Yes the ideal screw is all the back . My 93 is a auto .The spring is off a MACK truck so that's not the problem . Any ideas .. ????? New $475.00 now cheap ..
About 6 mounts back I got a TPIS 58 MM Throttle body off the forum looked new did all the work to install it on my 93 LT-1 auto ( lots of work ) it will not ideal any lower that 1500 RPM . Yes the ideal screw is all the back . My 93 is a auto .The spring is off a MACK truck so that's not the problem . Any ideas .. ????? New $475.00 now cheap ..
Idle screw doesn't set the idle. The ECM does. You probably have an air leak somewhere.
About 6 mounts back I got a TPIS 58 MM Throttle body off the forum looked new did all the work to install it on my 93 LT-1 auto ( lots of work ) it will not ideal any lower that 1500 RPM . Yes the ideal screw is all the back . My 93 is a auto .The spring is off a MACK truck so that's not the problem . Any ideas .. ????? New $475.00 now cheap ..
I put a BBK 52mm on my LT4 and had idle problems.
I don't know about the TPIS unit but you might want to take a look at the IAC circuit and compare it to the stock 48mm.
My BBK was totally different from stock.
I ended up making aluminum inserts that isolated the idle circuit passage from the twin throttle blades. Then drilled a hole 1/8") through the throttle body to copy the stock 48mm.
That brought the idle down but the idle still hunted (monitoring the IAC steps revealed that I was closer to stock but still not close enough).
I ended up taking my mini milling machine and duplicated the passages from the 48mm stocker and copied them into the BBK.
Yes a lot of work to get it running properly but it works well now.
I talked to Lloyd Elliot about this and he told me all aftermarket throttle bodies have idle problems.
If you look at the intake manifold for the LTx it has a hole on the bottom placed between the throttle blade openings. This hole distributes IAC signal to each intake port for smooth idle.
The aftermarket TB's blend the both ports which seems to screw up the idle.
Last edited by grandspt; Apr 17, 2020 at 04:03 AM.
Make sure the throttle plates are centered and allow the air to be blocked off. Loosen the screws that hold the throttle plates and allow the throttle to close. Make sure the plates find the center in the throttle bore and slowly tighten them. As noted make sure you have no air leaked and you iac is working and closing.
Don't know anything about an LT4 but my L98 did just fine idling with the Superram intake. That was before and after I installed headers. After which, I went to Lingenfelter for a tune to take advantage of the new mods and the tune woke it up. Granted that once it was tuned, all bets were off. I did reuse the Accel TB on the HSR and a few years after, I decided to change the TB to a Holley one because I did not want to rebuild the 58 mm Accel one. All the while, no issues with the idle.
Idle screw doesn't set the idle. The ECM does. You probably have an air leak somewhere.
The idle screw sets the minimium idle speed, so by backing it off he is making sure it can idle low enough to get down the desired idle which is not 1500 RPM.
The idle screw sets the minimium idle speed, so by backing it off he is making sure it can idle low enough to get down the desired idle which is not 1500 RPM.
I thought that we set the IAC up so the counts are not at 0 but at about 20-30 so that the ECM has adjustment via the IAC to increase the flow up or down to get the desired idle which is anywhere from 600 to whatever? An in his case, it is unlikely (unless something is wrong) to be at that 1500 mark?
Originally Posted by radar502
it will not ideal any lower that 1500 RPM . Yes the ideal screw is all the back
Also, with that, it is unable to close anymore to lessen the air coming in via the metered air leak or the IAC or am I mistaken?
Could a bad CTS reading cause the desired idle to be set at 1500?
I thought that we set the IAC up so the counts are not at 0 but at about 20-30 so that the ECM has adjustment via the IAC to increase the flow up or down to get the desired idle which is anywhere from 600 to whatever? An in his case, it is unlikely (unless something is wrong) to be at that 1500 mark?
Also, with that, it is unable to close anymore to lessen the air coming in via the metered air leak or the IAC or am I mistaken?
You are correct, but to get to the 20 to 30 count of the IAC you may have to back off the set screw to allow the throttle blades to close enough that the IAC has control. This is something that needs to be checked.
You are correct, but to get to the 20 to 30 count of the IAC you may have to back off the set screw to allow the throttle blades to close enough that the IAC has control. This is something that needs to be checked.
True. I think we are talking about the same thing but your expression was better than mine.
What needs to be checked? That the blades are actually closing although he has turned the screw OUT as far as it will go, based on my interpretation? Are you thinking that the blades are actually open although the should be closed since the screw is all the way OUT? Or are you thinking that the linkage is sticking or what? Maybe a visual of the blades so we can see if it really has a huge air gap at the top and bottom of the butterfly?
True. I think we are talking about the same thing but your expression was better than mine.
What needs to be checked? That the blades are actually closing although he has turned the screw OUT as far as it will go, based on my interpretation? Are you thinking that the blades are actually open although the should be closed since the screw is all the way OUT? Or are you thinking that the linkage is sticking or what? Maybe a visual of the blades so we can see if it really has a huge air gap at the top and bottom of the butterfly?
I mentioned that above in my first post. I have seen the throttle blades not closing all the way due to them not being centered in the throttle body bore. This will leave an air gap and cause a high idle situation. To solve this you need to center the blades in the bore when the throttle is closed, so there is no air leaks. You may have to back off the stop screw and then loosen the throttle blades, close the throttle all the way and then tighten the blades. After that reset the minimum idle speed with the stop screw and make sure your IAC is working and that you have no vacuum leaks.
Thanks for all the info ,but something else is going with the 58 mm deal . Wile is was running @1500 rpm I could push the throttle leaver back as hard as I could and it would drop down to 1000-800 rpm but when I let go it would go back to around 1500 rpm you could see like a very little movement in the balds like 16-32ent inch the movement was barely noticeable so it would go down to the desired RPM but would not stay there . I am thinking if bad throttle body or the blades a little off.They fit tight in the bores ?? PS the throttle cable not connected so that's not it . By it going back to the 1000/800 RPM I did not look any further that the throttle body .. I don't get it .
Was thinking's about buying another one ( after ALL the work I but in to this ) but with the info you guy sent ???? I am a good bolt on guy but all this other stuff ,I don't know if I could pull this off or not and looks like I am not the only ONE experiencing this .. as bad as I hate to might put the little throttle body back on and I as little after fooling with this 58-MM looks small .. I did get to drive it around the block running away but did and WOW big difference for sure .. No air leeks ,I reinstalled the ORG. one, runs great ..Lost for sure ..
as bad as I hate to might put the little throttle body back on and I as little after fooling with this 58-MM looks small .. I did get to drive it around the block running away but did and WOW big difference for sure .. No air leeks ,I reinstalled the ORG. one, runs great ..Lost for sure ..
I'm totally lost on what you are trying to say. Just guessing, you seem to think the 58 mm one looks bigger. It is. However, if you don't have the engine and supporting mods, I don't think it does more than look big. Kinda like a guy who is hung like a horse when limp but can't get it up. Not much good except for girls or some guys to look at.
If it runs well with the original one, perhaps that is the route you need to go unless you have the supporting mods. Which brings us to that question. What work have you done?
Hot cam ported heads headers 373 rear gear .. Am not a 18 year old kid been rodding for over 50 years . I need help not BS .. and yes the 58 MM is bigger 58 MM. Thanks ..
Hot cam ported heads headers 373 rear gear .. Am not a 18 year old kid been rodding for over 50 years . I need help not BS .. and yes the 58 MM is bigger 58 MM. Thanks ..
Then after 50 years you should know that bigger isn't always better. This is one of those cases since your stock TB can support what you are pushing out with that combination. IIRC, 400 is the limit so unless you have something else you didn't mention, all the 58 mm TB does is look pretty.
People are acting like installing a 58 MM throttle is a bad thing on modded but if anybody has read anything on this install BY the X-Perts not so bad and my motor is modded Hot cam ported heads headers and returned . I don't see the big deal ,like I said I drove it and pull you back in the seat way more pep for sure .
I may be old BUT not old school as some of you must be for the is it pretty comment .
I was thinking we were all on the same page trying to do improve or Corvettes no matter what we did to them and when someone needed REAL help with A REAL problem installing a 58 mm is not that big a deal people do it all the time ,I don't get it like ( I rebuilt this 93 from the ground up and rebuilt the motor ) Like I don't know what I am doing and some know it all .. Maybe I don"t need you help after all and some of you are A-holes ... Thanks but NO thanks ..
I am a carb. guy . I will figure it out ....
YEP PRETTY...
Thanks for all the info ,but something else is going with the 58 mm deal . Wile is was running @1500 rpm I could push the throttle leaver back as hard as I could and it would drop down to 1000-800 rpm but when I let go it would go back to around 1500 rpm you could see like a very little movement in the balds like 16-32ent inch the movement was barely noticeable so it would go down to the desired RPM but would not stay there . I am thinking if bad throttle body or the blades a little off.They fit tight in the bores ?? PS the throttle cable not connected so that's not it . By it going back to the 1000/800 RPM I did not look any further that the throttle body .. I don't get it .
Was thinking's about buying another one ( after ALL the work I but in to this ) but with the info you guy sent ???? I am a good bolt on guy but all this other stuff ,I don't know if I could pull this off or not and looks like I am not the only ONE experiencing this .. as bad as I hate to might put the little throttle body back on and I as little after fooling with this 58-MM looks small .. I did get to drive it around the block running away but did and WOW big difference for sure .. No air leeks ,I reinstalled the ORG. one, runs great ..Lost for sure ..
It seems to me that the blades are not centered, pull off the air inlet and take a few pictures of the closed throttle so we can see if there is an air gap and non centered blades.
People are acting like installing a 58 MM throttle is a bad thing on modded but if anybody has read anything on this install BY the X-Perts not so bad and my motor is modded Hot cam ported heads headers and returned . I don't see the big deal ,like I said I drove it and pull you back in the seat way more pep for sure .
I may be old BUT not old school as some of you must be for the is it pretty comment .
I was thinking we were all on the same page trying to do improve or Corvettes no matter what we did to them and when someone needed REAL help with A REAL problem installing a 58 mm is not that big a deal people do it all the time ,I don't get it like ( I rebuilt this 93 from the ground up and rebuilt the motor ) Like I don't know what I am doing and some know it all .. Maybe I don"t need you help after all and some of you are A-holes ... Thanks but NO thanks ..
I am a carb. guy . I will figure it out ....
YEP PRETTY...
Looks nice. A 58mm throttle body will not hurt performace and may help, lets work through the issue so we can get it to work for you. I run a 58mm on all of my engines or bigger. (Monoblade). If you are interested call me and I will walk you through what I am thinking.
Last edited by bjankuski; Apr 17, 2020 at 10:58 AM.
Yep centered I got in out in the light and pointed it at the sun NO light coming in around the blades .. I even tried to slid a small piece of paper in between the blades nothing .. Yep I was thinking the same but the balds tight . The bushing back on the throttle hard and it going down got me to thinking the blades too big MM to big .Its kinda like if the blades could go back one more MM it would be fine but springs back .. ?????
People are acting like installing a 58 MM throttle is a bad thing on modded but if anybody has read anything on this install BY the X-Perts not so bad and my motor is modded Hot cam ported heads headers and returned . I don't see the big deal ,like I said I drove it and pull you back in the seat way more pep for sure .
I may be old BUT not old school as some of you must be for the is it pretty comment .
I was thinking we were all on the same page trying to do improve or Corvettes no matter what we did to them and when someone needed REAL help with A REAL problem installing a 58 mm is not that big a deal people do it all the time ,I don't get it like ( I rebuilt this 93 from the ground up and rebuilt the motor ) Like I don't know what I am doing and some know it all .. Maybe I don"t need you help after all and some of you are A-holes ... Thanks but NO thanks ..
I am a carb. guy . I will figure it out ....
YEP PRETTY...
I'm sure it is way more pep. I believe it is called "The Placebo Effect". I haven't seen a dyno sheet proving that on that few mods, a 58 mm TB changes much but I'm sure there is one floating around.
You brought up your age first. That don't cut no ice in my book.
What's not to get? IF the motor doesn't need such a large TB as the stock one and as I understand, you switched back to a stock TB and the problem went away. Go back to the old one which is sufficient and opposed to the new one that is larger but unnecessary AND you have to try to make it work. Math is pretty simple to me.
I'm impressed by what works. Does the new TB work?
Sometimes one wants to try something different and I did not just say WOW $500.00 bucks for this pretty thing I got to have it deal . I did lots for reading and the X-perts said works and with some mods work better why I am I trying this is NOT the deal the fact that it won't work on my motor is the deal .WHY we all got Corvette in the first place and MODED for sure why you got those pretty wheels on that Corvette did not the old ones work . Give me a break .. I got work to do ..
TPIS 58 MM throttle help
