Throttle Problem "You Won't Believe This One"
Thread Starter
Burning Brakes
Joined: Aug 2001
Posts: 896
Likes: 1
From: Oro Valley AZ
Throttle Problem "You Won't Believe This One"
This is on a 1986 vert and it started after a car wash and the anti lock light came on and everything seemed to work ok and I can't locate the problem. Anyway at the same time I started to have a throttle hand up problem and posted it and I have checked linkage for bind and completely cleaned the throttle body and still it wn't go away. Today I
noticed when I hit the brakes it would drop the throttle. So while I was driving today it hung and I put it in neutral and it was at 1400rpm's and
them I taped the brakes and it dropped instantly. I tried this several times with the same results and when parked it, I hit the gas a little and say it hangs at 1000rpms andd I tap the brake it will drop to 600 and I did this several times with the same results from different rpm levels. This is beyond me as I have no idea what relationship there would be between the 2 issues. HELP would be appreciated !!!!
noticed when I hit the brakes it would drop the throttle. So while I was driving today it hung and I put it in neutral and it was at 1400rpm's and
them I taped the brakes and it dropped instantly. I tried this several times with the same results and when parked it, I hit the gas a little and say it hangs at 1000rpms andd I tap the brake it will drop to 600 and I did this several times with the same results from different rpm levels. This is beyond me as I have no idea what relationship there would be between the 2 issues. HELP would be appreciated !!!!
Le Mans Master
Joined: Aug 2003
Posts: 9,884
Likes: 3
From: Magnolia Mississippi
St. Jude '03-'04-'05-'06-'07
Very Strange, sorry i cannot be of any help... i'm sure someone will have already experienced this problem, or drive them all nuts till they figure it out. --- good luck ----
Race Director
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From: Almost all Skyline Cruises Vettes at Waterside 1-5
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Originally Posted by 1986vert
This is on a 1986 vert and it started after a car wash and the anti lock light came on and everything seemed to work ok and I can't locate the problem. Anyway at the same time I started to have a throttle hand up problem and posted it and I have checked linkage for bind and completely cleaned the throttle body and still it wn't go away. Today I
noticed when I hit the brakes it would drop the throttle. So while I was driving today it hung and I put it in neutral and it was at 1400rpm's and
them I taped the brakes and it dropped instantly. I tried this several times with the same results and when parked it, I hit the gas a little and say it hangs at 1000rpms andd I tap the brake it will drop to 600 and I did this several times with the same results from different rpm levels. This is beyond me as I have no idea what relationship there would be between the 2 issues. HELP would be appreciated !!!!
noticed when I hit the brakes it would drop the throttle. So while I was driving today it hung and I put it in neutral and it was at 1400rpm's and
them I taped the brakes and it dropped instantly. I tried this several times with the same results and when parked it, I hit the gas a little and say it hangs at 1000rpms andd I tap the brake it will drop to 600 and I did this several times with the same results from different rpm levels. This is beyond me as I have no idea what relationship there would be between the 2 issues. HELP would be appreciated !!!!
check your lines for leaks
Le Mans Master
Joined: Dec 2004
Posts: 5,789
Likes: 8
From: Myrtle Beach SC
St. Jude Donor '05-'06
On a vacuum related note I just got a Mityvac Silverline 4000 off eBay with all the attachments to do some serious vacuum checking as well as the brake bleeder attachments.Very nice product.
http://cgi.ebay.com/ebaymotors/ws/eB...BSAA%3AUS%3A11
http://cgi.ebay.com/ebaymotors/ws/eB...BSAA%3AUS%3A11
Pro
Joined: May 2005
Posts: 510
Likes: 0
From: crofton maryland
could the leakage from the curise control be hanging up, its controlled by the brake pedal, you know your doig 90 with the curise on and someone pulls out in front of you alls you do is hit the brakes and shuts it off. well just a thought????
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
The throttle can hang, if the throttle shaft is sticking in the worn out throttle shaft bores of the TB casting. More than one person has complained that the throttle would only stick while the engine was running. Not while it was shut off. As it turns out, the vacuum created behind the throttle blades was sucking the throttle shaft into the oblong portion of the bores. It's a long shot, but maybe the reduced vacuum as you apply the brakes is just enough to release the pressure on the throttle shaft. ???
RACE ON!!!
RACE ON!!!
Thread Starter
Burning Brakes
Joined: Aug 2001
Posts: 896
Likes: 1
From: Oro Valley AZ
I also checked the throttle shaft for play and it doesn't have any play, that was one of my first thought with it hanging. I also found that by hitting the throttle quick it will sometimes drop the idle back to normal, but not all of the time and touching the brake will drop it every time and also it isn't a cruise control issue, that is why I am stumped on this problem. It very well could be a vacumn issue but the system holds a constant vacumn pressure when I test it.
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Thread Starter
Burning Brakes
Joined: Aug 2001
Posts: 896
Likes: 1
From: Oro Valley AZ
It was at about 20 on my gauge at idle, but I am also wondering if there is anyway this could be ECM related, just to throw that into the mix ??? I can't see how, but I have had some really strange things happen on the older C3's I have had and even some on the Stingray series. I just don't know where to look that I haven't already tried and was it just unusual that it started at the same time as the anti lock problem ?? Or could there be some realationship ??
Thread Starter
Burning Brakes
Joined: Aug 2001
Posts: 896
Likes: 1
From: Oro Valley AZ
No problem that I can see when the engine is off, but I don't know how much movement will cause 800rpms differance. I assume it could be a very small amount. I removed the throttle cable and both the cable and the throttle body seems to be smooth.
Drifting
Joined: Aug 2004
Posts: 1,400
Likes: 0
From: Oceansaide CA
Brakes open a vacum purge solenoid. Try removing the throttle cable that goes from the cruise module to the throttle body. Also check for what CFI mentioned - the throttle blades will stick just a little bit open. I used a fat return spring to band-aid this.
Le Mans Master
Joined: May 2005
Posts: 5,214
Likes: 65
From: Queensland, AUSTRALIA
Originally Posted by rick lambert
Hope I read it right. A bad, or leaky brake booster will cause idle fluxuation when the pedal is depressed and released.
Yep,
. My 87 did that years ago and it was the booster diaphram had a small split in it. And also your cruise control cable might be too tight.
Thread Starter
Burning Brakes
Joined: Aug 2001
Posts: 896
Likes: 1
From: Oro Valley AZ
Believe it or not the problem is the throttle body, it was not going to the stop all the time when I let off the gas, so I put a bandage of a second spring until I find another throttle body. Thanks for all the help and suggestions.
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Originally Posted by CFI-EFI
The throttle can hang, if the throttle shaft is sticking in the worn out throttle shaft bores of the TB casting. More than one person has complained that the throttle would only stick while the engine was running. Not while it was shut off. As it turns out, the vacuum created behind the throttle blades was sucking the throttle shaft into the oblong portion of the bores. It's a long shot, but maybe the reduced vacuum as you apply the brakes is just enough to release the pressure on the throttle shaft. ???
RACE ON!!!
RACE ON!!!
