Help ! High Idle after acceleration - Team Camaro Tech
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post #1 of 13 (permalink) Old Feb 5th, 19, 04:15 PM Thread Starter
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Help ! High Idle after acceleration

Years ago my car was converted to power disc brakes. The brake booster was teed into the vacuum modulator. The car never stopped great. I have read this isn't a good thing to have it run this way. So I ran a new separate line from the booster to the manifold, a new line to the vacuum modulator line into the port on the front of the carb, and ran the pcv into the carbs large port in the back. Drove the car and the brakes definitely felt better. After getting on the car the idle went way up so I pulled over and shut the car off then restarted it and its fine. Ive been messing with it all day and drove it quite a bit. It hasn't done it since this morning. This happens sporadically.
The local parts stores here are out of the 11/32 brake booster line so I used a 3/8 pcv line for now for the brake booster vacuum line. Could the line be causing the issue ?
I used brake cleaner to test for vacuum leaks and I couldn't find anything, checked the manifold nipple baseplate spacers etc....

I Did just get the carb rebuilt ( pro form 650 double pumper ) also and it is running rich, I have to mess with it. I don't think the surge issue has anything to do with that though.

any ideas are appreciated thnx

69 camaro 350 pro form, double pumper 200r4

1969 Camaro 350 200r4 342 Posi
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post #2 of 13 (permalink) Old Feb 6th, 19, 04:05 AM
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Re: Help ! High Idle after acceleration

Well, if it was running rich with no vacuum leaks, then you have a small vacuum leak. This would cause engine to no longer run rich, which may raise engine speed. It's a bit of a long shot.

My guess is your throttle plate/linkage got stuck, did you try pulling accel pedal up with your foot? (assuming you still have factory solid linkage)

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post #3 of 13 (permalink) Old Feb 6th, 19, 04:10 AM
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Re: Help ! High Idle after acceleration

As you just re routed the booster hose maybe your throttle linkage is getting stuck by touching the hose?
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post #4 of 13 (permalink) Old Feb 6th, 19, 04:30 AM
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Re: Help ! High Idle after acceleration

Make sure your choke isnt staying slightly closed
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post #5 of 13 (permalink) Old Feb 6th, 19, 06:19 AM Thread Starter
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Thnx for the replies I’ll try that with the pedal. Going to reroute the booster so it’s totally away from the linkage. Just have to find the right hose now.

1969 Camaro 350 200r4 342 Posi
1987 WE4 Turbo Regal E85
2003 Sierra Stepside RCSB Belltech dropped


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post #6 of 13 (permalink) Old Feb 6th, 19, 07:19 AM
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Re: Help ! High Idle after acceleration

How is your return spring? When you manually turn the linkage under the hood, does it immediately come back and sit on the idle adjust screw?

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post #7 of 13 (permalink) Old Feb 6th, 19, 12:36 PM Thread Starter
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Re: Help ! High Idle after acceleration

Quote:
Originally Posted by HawkX66 View Post
How is your return spring? When you manually turn the linkage under the hood, does it immediately come back and sit on the idle adjust screw?
yes it comes right back to the original position

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2003 Sierra Stepside RCSB Belltech dropped


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post #8 of 13 (permalink) Old Feb 6th, 19, 01:13 PM Thread Starter
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Re: Help ! High Idle after acceleration

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Originally Posted by Vega$69 View Post
As you just re routed the booster hose maybe your throttle linkage is getting stuck by touching the hose?
I made sure it isn't touching and I also got the right power brake booster 11/32 hose still does it, its actually having the issue more often.
I tried to kick the pedal up did nothing.
Checked the booster check valve it is working as it should , so that's not it
I'm wondering if I have bad booster
I never had the issue when the brake vacuum line and the vacuum modulator were teed into each other but my brakes really didn't work well either. Since I ran the vacuum lines separate the brakes work better except when the car is having the issue and the idle is high then they feel like they used to.

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1987 WE4 Turbo Regal E85
2003 Sierra Stepside RCSB Belltech dropped


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Last edited by ME4NSTRK69; Feb 6th, 19 at 01:54 PM.
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post #9 of 13 (permalink) Old Feb 6th, 19, 04:29 PM
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Re: Help ! High Idle after acceleration

Power brakes work better because with the larger ID hose, more volume of vacuum.
I would disconnect and plug the booster vacuum line and test idle.
Yes brakes will require more pedal pressure, but you're looking for a lesser idle RPM.
If less, then leaky booster. Tried a hand vacuum pump on booster itself?

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post #10 of 13 (permalink) Old Feb 6th, 19, 05:21 PM Thread Starter
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Re: Help ! High Idle after acceleration

Quote:
Originally Posted by Everett#2390 View Post
Power brakes work better because with the larger ID hose, more volume of vacuum.
I would disconnect and plug the booster vacuum line and test idle.
Yes brakes will require more pedal pressure, but you're looking for a lesser idle RPM.
If less, then leaky booster. Tried a hand vacuum pump on booster itself?
I haven't tried the hand pump yet but its a good idea, I did plug the booster vacuum line and drive it. The car barely stopped so I didn't go too nuts driving it. It was too busy a day by me too many people around.
I want to get the carb tuned also its pretty rich at idle then it surges after getting on it.
If it is the booster then I am just going to wait until I do the hydro boost and call it a day for now.

1969 Camaro 350 200r4 342 Posi
1987 WE4 Turbo Regal E85
2003 Sierra Stepside RCSB Belltech dropped


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post #11 of 13 (permalink) Old Feb 9th, 19, 04:57 PM Thread Starter
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Re: Help ! High Idle after acceleration

Put a spacer in between the linkage connection to the carb to eliminate some play in the original rod, haven't driven it yet. Not sure if it is catching the cable but It is very close so even if it doesn't fix the issue less play in the linkage is still good.

1969 Camaro 350 200r4 342 Posi
1987 WE4 Turbo Regal E85
2003 Sierra Stepside RCSB Belltech dropped


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Last edited by ME4NSTRK69; Feb 9th, 19 at 05:45 PM.
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post #12 of 13 (permalink) Old Feb 9th, 19, 11:14 PM
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Re: Help ! High Idle after acceleration

Check your distributor mechanical advance springs. Iíve seen that cause fast idle when weaker aftermarket springs are used.

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post #13 of 13 (permalink) Old Feb 11th, 19, 03:16 AM
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Re: Help ! High Idle after acceleration

Quote:
Originally Posted by davidpozzi View Post
Check your distributor mechanical advance springs. Iíve seen that cause fast idle when weaker aftermarket springs are used.
Good point. I once forgot to remove the vacuum hose from the distributor when setting the advance, and could not figure out why I was not getting enough advance, or why the engine got to such a high idle when setting it to 8 degrees. I realized my mistake, unplugged the vacuum from the advance module, and it was much better when setting the initial timing!

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