throttle body leaking Smoke test
Thread Starter
Intermediate
Joined: Jan 2019
Posts: 37
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From: Athens TN
throttle body leaking Smoke test
I have been replacing bad vacuum lines on my 85 and decided to make a smoke machine to help locate them It worked great found quite a few my question is I have a lot of smoke coming out of the throttle body on the side by the return spring is this normal or something that can be fixed?
Melting Slicks
Joined: Nov 2013
Posts: 3,451
Likes: 336
From: Greater Cincinnati Area.
No, it's not normal. That's wear.
They can be re-bushed pretty easily and the kits are available on Ebay.
Here's a thread on the matter:
http://garage.grumpysperformance.com...bushing.10995/
Or, it is an excellent excuse to spend the money on an aftermarket TB if you want to.
Be sure to get the early one, because you need the TV cable provision to run your transmission pressure controls.
They can be re-bushed pretty easily and the kits are available on Ebay.
Here's a thread on the matter:
http://garage.grumpysperformance.com...bushing.10995/
Or, it is an excellent excuse to spend the money on an aftermarket TB if you want to.
Be sure to get the early one, because you need the TV cable provision to run your transmission pressure controls.
Last edited by confab; Mar 30, 2019 at 02:31 PM.
Melting Slicks
Joined: Nov 2013
Posts: 3,451
Likes: 336
From: Greater Cincinnati Area.
I don't know much about them, to be honest with you. I know BBK is very popular. I haven't heard anything bad about them.
The one I have I bought used, and I haven't installed it yet. It is a "Professional Products" I got from Pwnage, but I don't think they are in production any longer.
If it runs okay, you can always leave it like it is for now. But it is a vacuum leak. If you have idle issues that can certainly affect it.
On the newer cars you might be able to check the IAC counts and gauge the extent of the leak, but on our cars they enter "field service mode" when you connect the scanner and mess the datastream all up.
I do know that once they begin to wear, they get much worse with time. I have an extra stock body upstairs with really severe slop in it. So bad it rattles. Probably enough that it would never idle correctly regardless of any blade adjustment you made to correct it. So, replacing it or rebushing is probably in the future soon anyway.
You will absolutely want one for the 85-92 model years for the transmission pressure controls. It has to have those.
The one I have I bought used, and I haven't installed it yet. It is a "Professional Products" I got from Pwnage, but I don't think they are in production any longer.
If it runs okay, you can always leave it like it is for now. But it is a vacuum leak. If you have idle issues that can certainly affect it.
On the newer cars you might be able to check the IAC counts and gauge the extent of the leak, but on our cars they enter "field service mode" when you connect the scanner and mess the datastream all up.
I do know that once they begin to wear, they get much worse with time. I have an extra stock body upstairs with really severe slop in it. So bad it rattles. Probably enough that it would never idle correctly regardless of any blade adjustment you made to correct it. So, replacing it or rebushing is probably in the future soon anyway.
You will absolutely want one for the 85-92 model years for the transmission pressure controls. It has to have those.
Last edited by confab; Mar 30, 2019 at 04:00 PM.
Drifting
Joined: Dec 2012
Posts: 1,504
Likes: 73
From: Georgetown TX
If you buy bbk, you wii probably have to buy new smooth intake duct. The ome will not fit. Some have made them fit, but t had two and never could make them fit. That’s a another 40.00’
If you buy another tb, used are new, make sure it has the correct linkage on it. I think in 88 they changed.
I have bought several over the last several years, both new and used and was not happy with ANY of them. Most of the new cheaper ones have problems with the throttle plates not going back to idle after the engine warms up. It has happened to me numerous times
Fix yours and you will be much happier
If you buy another tb, used are new, make sure it has the correct linkage on it. I think in 88 they changed.
I have bought several over the last several years, both new and used and was not happy with ANY of them. Most of the new cheaper ones have problems with the throttle plates not going back to idle after the engine warms up. It has happened to me numerous times
Fix yours and you will be much happier
Thread Starter
Intermediate
Joined: Jan 2019
Posts: 37
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From: Athens TN
It does run fine but has a idle that goes 6-7-800 then back down 8-7-6 after warm up but I am still replacing vacuum lines just did a tune up and new IAC and TPS I will try it out as is before replacing throttle body or may just try the new shaft in mine.
Thread Starter
Intermediate
Joined: Jan 2019
Posts: 37
Likes: 0
From: Athens TN
I put it all back together and only fail on smoke test is on the spring side of the throttle body and I still have a crazy idle I have even cleaned out the vent line from gas tank still idling at 6-7-8 back 8-7-6 and will continue back and forth. I sprayed carb cleaner around TB spring and no change in idle. Any one have any other suggestions. Thanks
Melting Slicks
Joined: Nov 2013
Posts: 3,451
Likes: 336
From: Greater Cincinnati Area.
If you are sure you got all the vacuum leaks (And don't forget the brake booster) here are instructions for resetting the IAC and TPS:
https://www.corvetteforum.com/articl...ps-idle-speed/
BTW, I never could get mine to idle at anything below 650.
https://www.corvetteforum.com/articl...ps-idle-speed/
BTW, I never could get mine to idle at anything below 650.
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Melting Slicks
Joined: Nov 2013
Posts: 3,451
Likes: 336
From: Greater Cincinnati Area.
It is more difficult to get the throttle blade setting right on the 85, because you can't check IAC counts with a scanner.
But a little fiddling and you can make it work.
You might verify timing too.
But a little fiddling and you can make it work.
You might verify timing too.
Last edited by confab; Mar 31, 2019 at 04:57 PM.
Melting Slicks
Joined: Nov 2013
Posts: 3,451
Likes: 336
From: Greater Cincinnati Area.
Yeah, the computerized engine controls are great because they have given us access to performance that was always there, but tough to get at.. But, you have to work with them, not against them, and they have to be calibrated correctly.
Also, being an 85, if you have performance trouble you can't work out, you might want to check other things..
Among them: Water in the gas tank. (Took me forever to find this. Nobody expects it?) The fuel injectors are total crap in 85. (Bosch III's will retrofit if done right) The compression, of course. Other sensors. Even the ECM can be a problem. (I'm on my third) Etc..
Our cars are old and cranky, so it can take a little doing to get them all smoothed back out and running right. You'll get it.
Edited to add: There's an EST connector you unplug to set/check base timing. It's a single wire connector by the distributor.
Also, being an 85, if you have performance trouble you can't work out, you might want to check other things..
Among them: Water in the gas tank. (Took me forever to find this. Nobody expects it?) The fuel injectors are total crap in 85. (Bosch III's will retrofit if done right) The compression, of course. Other sensors. Even the ECM can be a problem. (I'm on my third) Etc..
Our cars are old and cranky, so it can take a little doing to get them all smoothed back out and running right. You'll get it.
Edited to add: There's an EST connector you unplug to set/check base timing. It's a single wire connector by the distributor.
Last edited by confab; Mar 31, 2019 at 05:22 PM.
Thread Starter
Intermediate
Joined: Jan 2019
Posts: 37
Likes: 0
From: Athens TN
Sounds like fun LOL good thing it runs good its just this crazy idle that im trying to figure out. The car was a gift from my brother-in-law I think he was trying to make me go crazy but I get her done Thank for the help
Thread Starter
Intermediate
Joined: Jan 2019
Posts: 37
Likes: 0
From: Athens TN
I have not measured vac I will what is a good reading and where is the best place to measure? it does have a little play you can grab the spring and rock it back and forth very small amount.
Team Owner
Joined: Dec 2000
Posts: 90,675
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From: SE NY
Cruise-In II Veteran
I pull a vac. line from the right side, insert a "T" and lay the gauge on windshield to check readings.
The gauge might even help resolve the potentially loose throttle rod issue.
The gauge might even help resolve the potentially loose throttle rod issue.
Safety Car
Joined: May 2001
Posts: 4,752
Likes: 1,642
From: Fairfax Virginia
Hello there Moved-to-TN!
I would take some play dough or soft clay and try to stop the leak on the throttle body shaft first to be sure that this particular leak is indeed the cause of your idle fluctuations. If you roll the clay into a string and wrap it around the shaft just to see if you can block the vacuum leak. If you idle smooths out and stabilizes at one speed then you are sure your bushings need to be replaced!
Years ago my throttle body was sticking and leaking anti-freeze so I bought the Professional Products throttle body. It works just fine and no real difference from the factory unit in performance. I should have just fixed my old throttle Body had I been smarter....
By the way!
Welcome To The Corvette Forum!
Good Luck and be sure to tell us what happens!
ctmccloskey a.k.a. Chris
I would take some play dough or soft clay and try to stop the leak on the throttle body shaft first to be sure that this particular leak is indeed the cause of your idle fluctuations. If you roll the clay into a string and wrap it around the shaft just to see if you can block the vacuum leak. If you idle smooths out and stabilizes at one speed then you are sure your bushings need to be replaced!
Years ago my throttle body was sticking and leaking anti-freeze so I bought the Professional Products throttle body. It works just fine and no real difference from the factory unit in performance. I should have just fixed my old throttle Body had I been smarter....
By the way!
Welcome To The Corvette Forum!
Good Luck and be sure to tell us what happens!
ctmccloskey a.k.a. Chris
Thread Starter
Intermediate
Joined: Jan 2019
Posts: 37
Likes: 0
From: Athens TN
I just did the complete setting of the timing and idle and TPS voltage and took it for a ride the idle is much better and it runs Great better than ever so for now I am going to live with it as is but may buy the bushing kit for the throttle body. Thanks for all the help
