79 Corvette Stalls when Idling
Thread Starter
Heel & Toe
Joined: Jul 2012
Posts: 24
Likes: 0
79 Corvette Stalls when Idling
Hey everyone,
I am having some issues with my vette stalling as it idles. If the car has been sitting for a while (over-night) it takes a while to start up and then has trouble not stalling when it's in idle. The ignition sounds like it's turning over every time but it takes a few tries for it to actually start. The problem seems to go away after I have driven it around for a while. After that, it runs kinda rough when it idles but it doesn't stall. Any ideas on how to fix this?
Here is a video of the problem.
http://www.youtube.com/watch?v=WlQHBqTrSVc
Thanks in advance,
Aaron
I am having some issues with my vette stalling as it idles. If the car has been sitting for a while (over-night) it takes a while to start up and then has trouble not stalling when it's in idle. The ignition sounds like it's turning over every time but it takes a few tries for it to actually start. The problem seems to go away after I have driven it around for a while. After that, it runs kinda rough when it idles but it doesn't stall. Any ideas on how to fix this?
Here is a video of the problem.
http://www.youtube.com/watch?v=WlQHBqTrSVc
Thanks in advance,
Aaron
Last edited by FreeTrainRide; Aug 2, 2012 at 07:29 PM.
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,391
From: At my Bar drinking and wrenching in Lafayette Colorado
Hey everyone,
I am having some issues with my vette stalling as it idles. If the car has been sitting for a while (over-night) it takes a while to start up and then has trouble not stalling when it's in idle. The ignition sounds like it's turning over every time but it takes a few tries for it to actually start. The problem seems to go away after I have driven it around for a while. After that, it runs kinda rough when it idles but it doesn't stall. Any ideas on how to fix this?
Thanks in advance,
Aaron
I am having some issues with my vette stalling as it idles. If the car has been sitting for a while (over-night) it takes a while to start up and then has trouble not stalling when it's in idle. The ignition sounds like it's turning over every time but it takes a few tries for it to actually start. The problem seems to go away after I have driven it around for a while. After that, it runs kinda rough when it idles but it doesn't stall. Any ideas on how to fix this?
Thanks in advance,
Aaron
- Incorrect timing
- Sticking centrifugal advance
- Ruptured or inoperable vacuum advance
- Vacuum advance hooked up to incorrect source
- Leaking fuel pump checkvalve
- Fuel logged float
- Incorrect float level
- Leaking well plugs
- Porous carb casting
- Incorrect choke setting
- Inoperable Choke Spring
- Missing choke hot air tubes
- Blocked exhaust crossover
- Inoperable heat riser valve
- Sticking or misadjusted choke linkage
- Misadjusted idle mixture screws
- Plugged idle air bleed passages
- Any missing/damaged/misadjusted carb components
- Valve train issues
Melting Slicks
Joined: Jul 2010
Posts: 2,762
Likes: 820
From: SUFFIELD CT USA 2023 C8 CORVETTE UN-MODIFIED FINALIST
2023 C8 of the Year Finalist - Unmodified
What is the out side temp when this happens and are you depressing the pedal to the floor once before starting. Remember a carb will not start like EFI. It needs a few minutes even in warm weather. Having your approximate location in your signature will also help us ! What RPM does it idle at when warm and not having the problem and what RPM does it idle at when it is having the problem?
Last edited by BPHORSEGUY; Aug 2, 2012 at 01:16 PM.
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Thread Starter
Heel & Toe
Joined: Jul 2012
Posts: 24
Likes: 0
I am in Colorado Springs. The weather has been in the 70's and 80's lately. A few days in the 60's. When the car is having the problem the rpm flutters right at/sightly above/and cuts out slightly below 5000. When it's not having the problem, it stays pretty solid just over 5000.
Melting Slicks
Joined: Jul 2010
Posts: 2,762
Likes: 820
From: SUFFIELD CT USA 2023 C8 CORVETTE UN-MODIFIED FINALIST
2023 C8 of the Year Finalist - Unmodified
I am in Colorado Springs. The weather has been in the 70's and 80's lately. A few days in the 60's. When the car is having the problem the rpm flutters right at/sightly above/and cuts out slightly below 5000. When it's not having the problem, it stays pretty solid just over 5000.
PS If you have the stock carb the idle adjust screw will be on the drivers side w/ the screw facing the front of the
car and you will need a medium size slotted screw driver to adjust it, takes just a few seconds
Last edited by BPHORSEGUY; Aug 2, 2012 at 05:50 PM.
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
If your idle in gear is 500 rpm, it's too low, it should probably be more like 650-750, 800-900 in park. Bringing up the idle a little will probably help out a lot, unless there are other problems. I don't like to set the idle in gear by myself, it makes me nervous to have it in gear with me not in the car, so I set it in park, I'd say around 900, and take it for a drive. Bring the idle, in park, down a little at a time, until you experience driveability problems, then bring it back up a little. It's time consuming, yes, but it works, and you can do it by yourself safely.
Once this is done, set the idle mixture using the idle mixture screws and a vacuum gauge. If this raises the idle, bring it back down using the idle speed screw. Good luck.
http://www.youtube.com/watch?v=XRCUibTkm3o
Keep the shiny side up!
Scott
Once this is done, set the idle mixture using the idle mixture screws and a vacuum gauge. If this raises the idle, bring it back down using the idle speed screw. Good luck.
http://www.youtube.com/watch?v=XRCUibTkm3o
Keep the shiny side up!
Scott
Thread Starter
Heel & Toe
Joined: Jul 2012
Posts: 24
Likes: 0
http://www.flickr.com/photos/7868262...in/photostream
http://www.flickr.com/photos/7868262...n/photostream/
Here are the pictures of my carb. Which screws need to be turned to adjust it?
I do appreciate all of you sticking with me through my issues. I'm still new at this.
http://www.flickr.com/photos/7868262...n/photostream/
Here are the pictures of my carb. Which screws need to be turned to adjust it?
I do appreciate all of you sticking with me through my issues. I'm still new at this.
Melting Slicks
Joined: Jul 2010
Posts: 2,762
Likes: 820
From: SUFFIELD CT USA 2023 C8 CORVETTE UN-MODIFIED FINALIST
2023 C8 of the Year Finalist - Unmodified
The idle screw will only be visible on the drivers side, side view.
Lets just start w/ the one idle speed screw, not screws, don't worry about the mixture screws yet. Get the car to idle at 800-900RPM in neutral and see if this helps. The screw will be on ths drivers SIDE not top of the carb w/ about a 1/4" dia. slotted head facing toward the radiator. Do you have an older friend or neighbor who was around when carbs were the norm??
Lets just start w/ the one idle speed screw, not screws, don't worry about the mixture screws yet. Get the car to idle at 800-900RPM in neutral and see if this helps. The screw will be on ths drivers SIDE not top of the carb w/ about a 1/4" dia. slotted head facing toward the radiator. Do you have an older friend or neighbor who was around when carbs were the norm??
Last edited by BPHORSEGUY; Aug 2, 2012 at 07:15 PM.
Thread Starter
Heel & Toe
Joined: Jul 2012
Posts: 24
Likes: 0
Here is the video.
http://www.youtube.com/watch?v=WlQHBqTrSVc
My view of the carb (driver side)
http://www.flickr.com/photos/7868262...in/photostream
http://www.youtube.com/watch?v=WlQHBqTrSVc
My view of the carb (driver side)
http://www.flickr.com/photos/7868262...in/photostream
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,391
From: At my Bar drinking and wrenching in Lafayette Colorado
The car should not take 10 seconds of cranking to start - it should start immediately with 2 pumps of the pedal, regardless of what the temperature is.
Why don't you just bring the car over and I'll set it up for you. If you don't know where the idle speed screw is, you really shouldn't be trying to "fix" the carb. And it's not likely that your problem can be fixed by turning a few screws - the "potential problem list" I provided above is real, and it's highly likely that your car is suffering from more than one of those issues: The idle speed didn't lower itself to 500 rpm - it's at 500 because there is some other problem causing it to be that low. Seriously.
Lars
Lafayette CO
V8FastCars@msn.com
Why don't you just bring the car over and I'll set it up for you. If you don't know where the idle speed screw is, you really shouldn't be trying to "fix" the carb. And it's not likely that your problem can be fixed by turning a few screws - the "potential problem list" I provided above is real, and it's highly likely that your car is suffering from more than one of those issues: The idle speed didn't lower itself to 500 rpm - it's at 500 because there is some other problem causing it to be that low. Seriously.
Lars
Lafayette CO
V8FastCars@msn.com
Last edited by lars; Aug 2, 2012 at 08:03 PM.
Melting Slicks
Joined: Jul 2010
Posts: 2,762
Likes: 820
From: SUFFIELD CT USA 2023 C8 CORVETTE UN-MODIFIED FINALIST
2023 C8 of the Year Finalist - Unmodified
Great video, it shows me 2 things. First your idle is way too low, set for 900RPM in neutral which should yield about 650-700 when you are in gear. Second, crank the engine for a good 10 seconds when you try to start rather then the 1-3 seconds you are cranking now, remember carb not EFI starting procedure. The idle screw is not visible in your pics, It is only visible from the drivers side w/ a front quartering view.Try searching Google for an idle screw ( not mixture screw pic ) or get a manual.
I just Googled "Quadrajet idle adjustment" and clicked "images" and it came up w/ an excellent sketch of what you need to find. Remember you are looking for the single idle adjustment screw not the 2 idle mixture screws, if you touch those w/ out a vacuum meter or some instruction you will really F____ things up and need a mechanic.
I just Googled "Quadrajet idle adjustment" and clicked "images" and it came up w/ an excellent sketch of what you need to find. Remember you are looking for the single idle adjustment screw not the 2 idle mixture screws, if you touch those w/ out a vacuum meter or some instruction you will really F____ things up and need a mechanic.
Last edited by BPHORSEGUY; Aug 2, 2012 at 07:46 PM.
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
I actually don't think that idle is too low. I suspect other issues.
My 78 runs fine with very similar specs, and I'm running a 216/216 110 cam.
It'll stay alive down to slightly less than that when it's still cold.
My 78 runs fine with very similar specs, and I'm running a 216/216 110 cam.
It'll stay alive down to slightly less than that when it's still cold.
Melting Slicks
Joined: Jul 2010
Posts: 2,762
Likes: 820
From: SUFFIELD CT USA 2023 C8 CORVETTE UN-MODIFIED FINALIST
2023 C8 of the Year Finalist - Unmodified
I just saw where Lars offered to setup the motor for you and I assume you 2 are close enough to make it happen. That is a deal that most of us would jump on in a heartbeat. Your car will run the best it can and you will learn a ton in the process. I say get that car to Lars as fast as you can!!!!