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High idle

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LarryBible

Guest
I have not had a chance to get into it yet, but my L98 began idling at about 1400 RPM. This has intermittently occurred in the past, and could be brought down by pressing on the point where the throttle cable connects to the throttle plat actuator. I assume this is true now.

The throttle body is clean when looking at it, but I have not taken the throttle body apart. Has anyone seen this caused by an internally dirty throttle body, or hanging cable? where can I get a throttle body repair kit?

Thanks for sharing any experiences you may have with this.

Have a great day,
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Larry ( WELCOME TO CAC!!!)

I think it's time to replace ( Rebuild ) your Throttle body assy.

Grab the linkage on the right side of the TB and see if you can wiggle it up & down.

If you can.. the side bushings are failing
(failed) and the butterflys and hanging into the cast of the body....

I had mine rebushed @ the local carb repair shop ( but they are GOOD )

I think it was $125.00 which was almost the bail out point.... the rest of the TB was perfect and I had already done the TPS & the IAC.

So without a picture.. or the car in front of me that's the best advise I can give you.



Vig!
 
S

Shadowing1985v

Guest
hmm

so thats another thing that could be wrong with my 85

after i put on 30 pound injectors and the adjustable fuel regulator, that sounds like the next thing i need to look at

they arrive on saturday, i hope, that is


my L98 started idling at 800 and i have been repairing things and have slowly worked the idle to 500 since of last week

i stil have another 100 more to go
 
L

LarryBible

Guest
Thanks for the response. I am not at all afraid of tackling the throttle rebuild if I can find the kit. I suppose I can go to the Chevy house, but it's always a pain to go there, order and then come back later.

Does anyone know where I can buy a throttle body rebuild kit online?

About two years ago I looked for a Forum like this on Corvettes and was not successful. The only ones I found had NO mechanical understanding. All they knew was where there next club meeting would be and the color of their car.

This site is EXACTLY what I've been looking for. Get ready for me to wear you guys out with questions. Maybe I can offer an answer here and there too.

Have a great day,
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Throttle body

There's no "Kit" as in a carb rebuild kit...

These guys are true machinist's and will make the parts from scratch ( bronze dowel stock...)

To make the new bushings....

since they all wear differently... hard to design a one kit fits all deal.

Vig!
 
S

Shadowing1985v

Guest
hey vig

what do you mean by wiggling the leakage up and down


like frontward and backward "front of the car to back of car or side to side: wheel to TB??
 
L

LarryBible

Guest
You are wiggling the throttle shaft against the bushing to check for the shaft being loose against the bushing.

So, what I'm hearing is that there is no bushing already in place. It would have been very inexpensive for GM to put a Delrin bushing in these positions so you could simply push it out and put in a replacement. Doh!... where's my head, that would have cost an additional $0.50 per car.

Thanks for the responses,
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
My understanding

That the cross shaft just rides in the POT metal of the casting.. and when it goes it's gone....unless you have GOOD people to machine out the casting and refit as needed.


Yeah I agree, Kinda cheep


Vig!
 

fixvet

Well-known member
Joined
Apr 4, 2002
Messages
139
Location
Clever, MO
Corvette
1998 Two Tone Torch Red& Black Coupe
I'd clean the IAC real good before tearing into the throttle body.
The IAC on the bottom/passenger side of the TB controls your basic idle setup. It's an easy fix.
Good luck
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Repost the problem.

"But my L98 began idling at about 1400 RPM. This has intermittently occurred in the past, and could be brought down by pressing on the point where the throttle cable connects to the throttle plate actuator. "

This to me states that the butterflys are getting stuck OR the return spring is jamming the wornout mechinism allowing it not to close properly.


Vig!
 

WhalePirot

Well-known member
Joined
May 9, 2002
Messages
2,942
Location
SoCA
Corvette
1984 White Z-51/ZF6-40/Shinoda body
Vacuum leak elsewhere?

Unmetered fuel or air really messes up the computerized cars.

The basics still apply. While 'choking down' the air inflow will idle it down, perhaps a sucking sound, or the WD-40 search tool will reveal a vacuum leak elsewhere.
 
S

Shadowing1985v

Guest
i did a no no

when i cleaned my TB out, i didn't think about undoing the 6 screws on top and cleaning under the plate, hehe

my TB was like the dirtiest TB ever, the IAC had all this black crap in side of it,,,

i took a tooth brush to it

but still didn't get all the black out of it,,,
its not durting just kinda molded on there

should i take it back off and soak it over nite, or do u guys think it will be alright " I mean should i make it all shiny"
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
That's why the grab trick

So to re explain it......


You grab the shaft where the throttle cable is clipped to..... move it ... up / down / Fwd / Back to see if the shaft has ANY slop in it... the more the slop... the more air leaks....

And as an extra bonus......

If the shaft has to much slop in it the butterflys will try to dig a new area in the POT METAL CASTING of the intake ports causing sticking of the plates...

You can remove the snorkle.. and look down the ports...... Open the butterflys up and take a look......

This whole procedure will take less than 10 minutes, time well spent!

Vig!
 
L

LarryBible

Guest
I have grabbed the shaft and there is some slack. I have not been able to explore further because I had wisdom teeth cut out Friday. Maybe next weekend. It also could be a hose or something causing a leak. If so, it is intermittent.

I think I can get further into it next weekend.

BTW, in the course of looking into a fix for worn throttle shafts I learned that the BBK throttle body has ball bearings and o-rings on the shaft. This is the way GM should have built it in the first place.

Thanks all,
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
OUCH

That will leave a mark.....


Let us know!!!!

Vig!
 
L

LarryBible

Guest
Standard makes a throttle body gasket kit and it sells for $9. I completely disassembled the the TB yesterday, thinking that if the shaft is loose I will have it bushed or get another one. The shaft was in good shape and overall the unit wasn't ridiculously dirty.

I also was a little past due in flushing the cooling system, so this was the obvious time to do that. In the course of flushing the cooling system, I just put the TPS back where I thought that it originally was and the idle is now worse.

I can't find a vacuum leak anywhere, but once I finish flushing the cooling system enough to get it all back together, I'll set the TPS at 540 milliVolts and continue searching for the idle problem.

I think it is set too low and/or there is a problem with the flexible snout between MAF and TB. I think this because it set a 22 and 34. My reading indicates that if no voltage is seen from the TPS it will cause a condition that also appears to be unmetered air.

Good news is that the TB shaft and bores are okay, bad news is working through the high idle problem.

Thanks for your comments,
 
D

DHOUGHTON

Guest
Idle too high simple check and fix...

O.K. Lets get untechnical for just a moment. Start your car and when your idle gets to 1400 pop the hood. Now look at the cables where they connect to the TB. Now is the throttle off the
adjustment screw by a little bit. What happens when you push the throttle up, does the idle drop back down to normal? If this is the case your spring is probably whimpey. GO to the hardware store and buy a 3 or 4 inch spring about the same roundness as a pencil. Hook it up
to the TB to supplement the tension using wire ties. Play with the tension a little at a time. It works great on my 90 vette. GOOD LUCK TO YOU.

Marathoner
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Hey not bad

That will mask the problem..or fix a spring that has snapped... i'll have to ponder the implimentation... a TY WRAP... I think we can do better than that....

Are all the cables well oiled... do the butterflys move freely & SNAP back into place?


Vig!
 
L

LarryBible

Guest
Thanks for the replies.

The throttle shaft is very positively against the stop now. There is no cable binding or anything like that. That part seems much better than it was before.

I may have been premature posting this before getting the TPS properly adjusted to see the results of that. It very well may be that all is fine after the TPS is properly adjusted.

I can't tend to it this afternoon, but hopefully will get to it one night this week.

Thanks again,
 

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