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Discussion Starter #1 (Edited)
Hey all, I have a 1965 mustang with a Edelbrock 600 cfm carb and I recently started noticing a louder noise than usual when I have my car on park and when I go from park to reverse it slams into reverse as if I was trying to peel out. When I switch to another gear it goes back to normal although it seems like the idle speed is high now.

Any suggestions on what to do?

Edit: To add on, while I was on a red light yesterday I switched to park and when I went to back to drive it wouldn't move at all. I had to turn off and on the car to get going again.
 

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You may have developed a vacuum leak. Spray carb cleaner around the base of the carb, around the intake, the PCV hose and the fitting, line, and short hose on the trans for the modulator valve. If it makes no difference, then, yeah, turn the idle speed screw on the driver side counterclockwise until the idle comes down and re-tune timing, idle mixture, and final idle speed from there.
 

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Before you start twisting screws, check for a vacuum leak as mfc66 noted, and make sure your choke is disengaging fully. You'll also want to verify that your static timing hasn't drifted. Verify that your distributor hold down clamp is tight, and check your timing at idle.

Idle screws don't move on their own, so something else is causing the problem.
 

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HK is right on this. Don’t fix the symptom, you should find the root cause for the change and fix that first. Plenty of things to check first before you make compensating adjustments that may mask your real problem.
 

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Normally a vacuum leak on a carbureted vehicle makes it idle rough and slower not faster unless it was already too rich before the leak developed. Fuel injection is the opposite. A vaccum leak makes the idle go up.

Like others said make sure the choke is coming off of fast idle. The timing has not changed. Nothing is binding in the carb linkage. Throttle return spring is there. If you can't find anything what changed, because obviously something did you can always readjust the idle speed screw. Idle speed can very a little with a carburetor with atmospheric changes but this sounds like too much or rpm change for that.

The part about it not moving after you put it in park and then back to drive is strange. Check the trans fluid level? I have not worked on C4 automatics, mostly Chrylser and GM automatics but they all work about the same way. There is a vacuum modulator valve and a governor that control the operating pressures that perform the automatic shifting of the transmission. If you had a vacuum modulator valve go bad or the vacuum hose to it had a leak that would make the trans shift real harsh. That would be considered a vacuum leak but it would not "normally" raise the idle. If you pull that vacuum line off of the intake manifold and apply a handheld vacuum pump to it, it should hold vacuum.

I'm not sure it would have anything to do with it not moving after putting it in and out of park? Its possible you more than one problem going here.
 

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Good info above. Your idle should be set so when the tranny is in reverse the motor is at 600 rpm.
 
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