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New guy, here. Ran into trouble a while back with SoCal emissions and left my beloved 1984 Mustang GT sitting for years. Too many years, apparently. Have begun restoration, spent boo-koo bucks front to back bumper. Now, after being tossed out of most every shop in town, I'm told I have an undiagnosable vacuum problem leaving me with cold start issues. After ten minutes fluttering the gas pedal, stall and start, eventually runs great. Along the way, I've spent over $500 replacing ALL vacuum lines. Like I said, 1984, GT 5.0, four-barrel Holley carb. BTW - temp gauge scarcely gets above lowest normal reading. Any help is greatly appreciated. jb
 

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These people are trying to tell you there is vacuum leak when the vehicle is cold but not when its warm? And Its a big enough of a vacuum leak that a closed choke can not compensate for it? If its that big of a leak you should be able to find it quickly using propane or by pinching off or disconnecting anything vacuum related. Eliminate every manifold vacuum hose connection going to the carb and the intake. Brake booster, charcoal canister, anything connected to intake manifold vacuum. If that does not temporarily solve your problem. Then the only thing left is a leak at the intake or carb and they could be easily found with propane being applied along the gaskets. I did have one that had an intake gasket leak in the lifter valley. That one I found by pulling the PCV out of the valve cover and sticking a piece of paper over the valve cover hole. It sucked the paper up against the valve cover so I that told me there was an internal vacuum leak.


How do they know it has a vacuum leak if they can't find the leak? None of this makes since??????? Y

I'm thinking its more of something like the vacuum hose routing being wrong to an EGR valve, in combination with a faulty thermostatically controlled vacuum switch. Something like that. I would verify all the vacuum hoses are hooked up correctly and the thermostatic vacuum switches are opening and closing when they should.

Try pulling the hose off the EGR valve and plug the hose when its cold and see if it makes a difference. The engine will fall on its face and stumble if it opens at idle.

It should have an under hood emissions label with vacuum schematic that looks similar to this one. It was there at one time. Ford likes to use color coded plastic vacuum lines that most people refer to as spaghetti because the second you touch them they snap like a piece of un-cooked spaghetti. Over time it all goes bad and people replace it with regular vacuum hose. Its real easy to start mixing up hoses when they are no longer color coded. There are probably several temperature controlled vacuum switches which make me think that one of them might be your problem.
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Could be a faulty vacuum canister or EGR valve diaphragm I guess, controlled by ported vacuum switch temp to change positions then clear up.
 

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Discussion Starter #4
These people are trying to tell you there is vacuum leak when the vehicle is cold but not when its warm? And Its a big enough of a vacuum leak that a closed choke can not compensate for it? If its that big of a leak you should be able to find it quickly using propane or by pinching off or disconnecting anything vacuum related. Eliminate every manifold vacuum hose connection going to the carb and the intake. Brake booster, charcoal canister, anything connected to intake manifold vacuum. If that does not temporarily solve your problem. Then the only thing left is a leak at the intake or carb and they could be easily found with propane being applied along the gaskets. I did have one that had an intake gasket leak in the lifter valley. That one I found by pulling the PCV out of the valve cover and sticking a piece of paper over the valve cover hole. It sucked the paper up against the valve cover so I that told me there was an internal vacuum leak.


How do they know it has a vacuum leak if they can't find the leak? None of this makes since??????? Y

I'm thinking its more of something like the vacuum hose routing being wrong to an EGR valve, in combination with a faulty thermostatically controlled vacuum switch. Something like that. I would verify all the vacuum hoses are hooked up correctly and the thermostatic vacuum switches are opening and closing when they should.

Try pulling the hose off the EGR valve and plug the hose when its cold and see if it makes a difference. The engine will fall on its face and stumble if it opens at idle.

It should have an under hood emissions label with vacuum schematic that looks similar to this one. It was there at one time. Ford likes to use color coded plastic vacuum lines that most people refer to as spaghetti because the second you touch them they snap like a piece of un-cooked spaghetti. Over time it all goes bad and people replace it with regular vacuum hose. Its real easy to start mixing up hoses when they are no longer color coded. There are probably several temperature controlled vacuum switches which make me think that one of them might be your problem.
View attachment 746761
Thanks for all the "ammunition" to deal with these folks. They're the top notch repair shop in my area. Not ripoffs. Perhaps there isn't a mechanic in the house who was born before 1984. Again, thanks. jb
 

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65 Fastback 289 4 spd, 65 convertible 5.0L 5 spd. 3.73 8.8
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New guy, here. Ran into trouble a while back with SoCal emissions and left my beloved 1984 Mustang GT sitting for years. Too many years, apparently. Have begun restoration, spent boo-koo bucks front to back bumper. Now, after being tossed out of most every shop in town, I'm told I have an undiagnosable vacuum problem leaving me with cold start issues. After ten minutes fluttering the gas pedal, stall and start, eventually runs great. Along the way, I've spent over $500 replacing ALL vacuum lines. Like I said, 1984, GT 5.0, four-barrel Holley carb. BTW - temp gauge scarcely gets above lowest normal reading. Any help is greatly appreciated. jb
Has the shop used a smoke machine to look for vacuum leaks? EGR could be stuck open a little. Sounds like it could be a carb problem. Does it squirt fuel by just opening the throttle without cranking? Is it getting fuel to carb? Its been sitting for a while, is the tank full of crap?
 

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JMO, Been at this problem for a while. Tank was pulled, inspected. Carb' rebuilt, twice. What I did forget to mention after this repair shop replaced ALL vacuum lines, the car ran GREAT. Weeks later, I had a stall out of nowhere. Took it in, couldn't find that problem. After, it was a bear to start. Once running hot, runs fine. Thanks for taking the time to ask. jb
 
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