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Throttle Body

Lucs_Vette

Member
Joined
Mar 1, 2006
Messages
24
Location
Kemptville, Ontario
Corvette
1985 Black Coupe
Well i'm back again for a new season after my car and i have been hibernating for the winter .. LOL

Have anyone of you ever experienced a stick throttle body? and what have you done to fix it and was it successful?

Here is my situation: i start my car .. not a problem .. as it warms up .. and i play with the throttle .. it doesn't always go back to idle .. i have to slap the pedal .. ans some times a few times before it goes back to idle. When the engine is at running temperature .. it seems to get worse .. making shifting a challenge .. (manual tranny). My mechanic has cleaned out the ports .. which has improved it by about 40%. i don't know about any of you .. but this is really starting to annoy me to the point where i don't drive it as much as i want to .. and that is often .. lol

any pointers other then replacing to whole body. any help would be much appreciated

Thanks
 

Rod Brown

Active member
Joined
Dec 31, 2004
Messages
39
Location
L.A.,CAL.
Corvette
2016 Blacki Sting Ray
Maybe?

Suggestion: Have you lubed the gas pedal under the dash? might be sticking.worth a try
 

Lucs_Vette

Member
Joined
Mar 1, 2006
Messages
24
Location
Kemptville, Ontario
Corvette
1985 Black Coupe
I've done all of that .. it sticks on the throttle body internal flaps (or whatever they are called .. lolll).

if you move the throttle directly on the body it self it sticks .. which removes all possibility its the cable or pedal .. i've already lubed it as a first step.

i was told that i should sand down the ports where the flap sticks, but i need to know if anyone has ever tried this and where they successful.

Thanks
 
S

speedmaster4

Guest
do not attack the throttle body with abrasives...if you can see corrosion there, gently scrape it off with a dull boy scout knife...put some 'marvel mystery oil' on the throttle shaft from inside the throttlebody and outside and allow it to soak in overnight, then oil again and work the blades full stroke a few dozen times by hand.

don't use wd-4o or similar sprays, absolutely nothing with silicone (goodbye o2 sensor)
 

SPANISHVETTS

Well-known member
Joined
Nov 5, 2002
Messages
1,143
Location
El puerto de Santa Maria Spain
Corvette
before 60,63&82 now 90 383 Stroker & 91 ZR1-Sold
This is a common C4 problem. There are no bushings on the throttle shaft. The rod that the butterflies are mounted on are in direct contact with the aluminum TB so the aluminum wears away which lets un-metered air into the intake and causes the butterflies to stick.

Several years ago I posted a how to about modifying the TB by installing sealed roller bearings. It is not a hard job but it does require either a procession drill press or a lathe. Any decent machine shop should do the job for $40-$50 or you can buy a modified TB on eBay. There is one guy who has been selling them on eBay for years. The B&K after market TBs come with roller bearings on the throttle shaft.

Here is a pic of the TB machined to accept the bearing. The roller bearing is in the lower rt of the photo.
TBNEW1.JPG
 

OSU-VETTE

Well-known member
Joined
Jan 19, 2003
Messages
60
Location
Central OH
Corvette
1985 Z51, Black with Purple Accents
Here is a pic of the TB machined to accept the bearing. The roller bearing is in the lower rt of the photo.


Can you send the image and possibly more details either online or to me? wallacej@rrohio.com.

I have a very similar problem and prefer to rebuild my throttle body vs purchase a new one (or a used one and still have to rebuild it!)

Thanks.
 

kalmwill

Active member
Joined
Feb 13, 2003
Messages
38
Location
Toronto
Corvette
1986 Bright Red Coupe
Can you include me into the information loop. My 86 Corvette has the same problem. There is a local carb shop that instals brass bushings but I can see that the same problem will redevelop as the bushings will wear just as the original material on the throttle body. Bearings are a much better solution. Where can one obtain the bearings that you have pictured in your reply. Any help would be much appreciated. Thanks
 

SPANISHVETTS

Well-known member
Joined
Nov 5, 2002
Messages
1,143
Location
El puerto de Santa Maria Spain
Corvette
before 60,63&82 now 90 383 Stroker & 91 ZR1-Sold
L-98 Throttlebody mods.

Can you include me into the information loop. My 86 Corvette has the same problem. There is a local carb shop that instals brass bushings but I can see that the same problem will redevelop as the bushings will wear just as the original material on the throttle body. Bearings are a much better solution. Where can one obtain the bearings that you have pictured in your reply. Any help would be much appreciated. Thanks
I source anything that I can not find locally through
http://www.globalspec.com/ but you should be able to find the bearings at supply house that specializes in power transfer or google for roller bearings.
http://www.globalspec.com/

I did this on the PDA on the train yesterday and I am not a great thumb typist so forgive the typos and spelling.

L-98 Throttlebody mods.

The L-98 & LT-1 TBs have a common problem of the throttle shaft wearing the aluminum body because there is no bushing or bearing between the TB and the steel shaft.

The cure is to install bearings and seals into TB. You will need a Dremal or small die grinder and either a Mill, Lathe or precision drill press and a end mill.

Dissemble of the TB: (Take photos and make notes of how the bell cranks and springs fit or you will have a lot of fun putting it back together.

The butterflies are held onto the throttle shaft by 4 screws. The back side of the screws are braded down so that they can not come lose and enter the engine. Use the Dremal to grind the braded part of the screws away. Grind only the screws – not the throttle shaft.

Remove the IAC and TPS from the TB

Remove the screws and the butterfly plates.

Dissemble the bell crank and springs from the left side of the TB by grinding the braded down end of the throttle shaft so that the bell cranks can be removed. Do not go wild with the Dremal grind just enough so that the bell crank can be removed. The assembly varies from year to year so make notes.

Remove the nut and spacers that holds the throttle shaft in place and remove the shaft from the TPS side of the TB.

Modifications

Take the shaft to your friendly bearing shop and find the smallest outside diameter sealed roller bearing that will fit the shaft. I think that the largest OD bearing that you can us is 10mm but memory fails me for the exact size. The roller bearing can be no more than 12mm long. Buy 2 of these.

Buy an end mill the same diameter as the bearings.

Buy at least 5 new screws to replace the 4 you removed from the butterflies plus 1 more for the end of the throttle shaft, a small washer to fit this screw and a drill and tap for this screw.

Drill and tap the end of the throttle shaft where you ground it away on the bell crank end.

With the end mill in either the mill, precision drill press, or lathe cut the throttle shaft passage on both sides of the TB to 0.1mm deeper than the length of the roller bearings.

Gently press the bearings into the TB.

Insert the Throttle shaft from the TPS side of the TB.

Reassemble the bell crank side of the TB with all of its springs and spacers and tie it all together with the small washer and screw. (Aren’t you glad that you took pictures and made notes?)

Reinstall the butterflies and brad down the back side of the screws so that they can not possibly come lose. Be careful and do not bend the throttle shaft when you brad down the screws. The safest way is to support the butterfly and shaft with a dowel that will just fit into the TB opening.

Reinstall the IAC and TPS.

Congratulations you now have a new TB that works without friction and does not leak.

Hobby and Model shops may have a good selection of small bearings as well as the equipment to do the machine work.

I think that you could probably have the machine work done in a shop for about the same price as buying the end mill, etc.
 

OSU-VETTE

Well-known member
Joined
Jan 19, 2003
Messages
60
Location
Central OH
Corvette
1985 Z51, Black with Purple Accents
Igeaux,


Thanks for putting this together, you are giving me the confidence to tackle this job myself! Nothing ventured, nothing learned....
 

kalmwill

Active member
Joined
Feb 13, 2003
Messages
38
Location
Toronto
Corvette
1986 Bright Red Coupe
Thank you for taking the time to writeout detailed instructions. your effort is much appreciated. Many thanks
 

Lucs_Vette

Member
Joined
Mar 1, 2006
Messages
24
Location
Kemptville, Ontario
Corvette
1985 Black Coupe
Hi, i was just on Ebay and found rebuilt Throttle Bodies. the store id is xtreme-fi. does anyone have any comments before i click the buy now button.

Any feedback is much appreciated .. thanks
 

SPANISHVETTS

Well-known member
Joined
Nov 5, 2002
Messages
1,143
Location
El puerto de Santa Maria Spain
Corvette
before 60,63&82 now 90 383 Stroker & 91 ZR1-Sold
Hi, i was just on Ebay and found rebuilt Throttle Bodies. the store id is xtreme-fi. does anyone have any comments before i click the buy now button.

Any feedback is much appreciated .. thanks


I just had a look at the eBay store. The product looks good and the price is right. With the $60 core refund it brings the price down to $159... Just think of it as Dinner for 4 at a decent restaurant.

I did not see any TPI TBs on his site. Maybe you already bought it.:confused

The LT-1 TB will fit the TPI plenum but you will have some vacuum line and linkage problems.

He states that the bearings have been repaired but he does not say how. I would ask if he has installed bearings and seals, bushings, or repaired the bearings by some other means.

:eek:hnoesI see that he has some TB bored out to 54mm. I would stay away from these like I stay away from Rattlesnakes. I picked up a few junk TBs to play with and tried to bore them more than 52mm using a $275,000 Mori Seiki CNC lathe without success. The casting is just too thin to support more than 52MM. I got out to almost 53 MM but the skin was paper thin and I would never trust it. I even tried boring the TB with new centers to save some of the aluminum on the outside of the casting but ended up leaving the IAC passage less than 0.1MM thick. I am not an expert machinist but it is hard to make a mistake on a simple boring job with the Mori.

:upthumbsThe stock TB bore out ok to 52MM on any old lathe or mill so I would buy his 52MM if I bought one of his products.
 

SPANISHVETTS

Well-known member
Joined
Nov 5, 2002
Messages
1,143
Location
El puerto de Santa Maria Spain
Corvette
before 60,63&82 now 90 383 Stroker & 91 ZR1-Sold
Here are some more photos I found of the modified TB and throttle shaft.

You can see how the throttle shaft is cleaned up, drilled and tapped to take the retainer screw to hold on the bell crank and the sealed roller bearing. Sorry, I can't remember the part # of the bearing.:W

new_TB_copy.jpg

cat
 

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