1957, engine suddenly surging at idle | Ford Thunderbird forum club group 1955-2005 models

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1957, engine suddenly surging at idle

vernz

vernz

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1957
My 1957, stock D code 312, came out of hibernation yesterday. It started and restarted perfectly and ran well for about 1.5 hours which included a couple of stops of 20 minutes to 1/2 hour. Then, at a stop sign it suddenly started surging from about 700 to 200 RPM. It did stall once, but that may be from my clumsy attempts at keeping it going. After that it did not stall, but I was running stop signs rather than giving it a chance to stall. The engine temperature was consistently in the normal range and the outside temperature was in the high 60's. I am running standard point ignition. I fueled it up with premium non-ethanol gas plus lead substitute just before starting the excursion. I fueled up another car at the same station with the same fuel and that car ran fine. After the surging problem at idle it seemed to run OK at speed. The next morning I started the car and it continues to surge at idle (at least it isn't an intermittent problem). The carburetor was professionally rebuilt about 2 years ago. Any thoughts on what I should check first? Thanks, Vern

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vernz said:
My 1957, stock D code 312, came out of hibernation yesterday. It started and restarted perfectly and ran well for about 1.5 hours which included a couple of stops of 20 minutes to 1/2 hour. Then, at a stop sign it suddenly started surging from about 700 to 200 RPM. It did stall once, but that may be from my clumsy attempts at keeping it going. After that it did not stall, but I was running stop signs rather than giving it a chance to stall. The engine temperature was consistently in the normal range and the outside temperature was in the high 60's. I am running standard point ignition. I fueled it up with premium non-ethanol gas plus lead substitute just before starting the excursion. I fueled up another car at the same station with the same fuel and that car ran fine. After the surging problem at idle it seemed to run OK at speed. The next morning I started the car and it continues to surge at idle (at least it isn't an intermittent problem). The carburetor was professionally rebuilt about 2 years ago. Any thoughts on what I should check first? Thanks, Vern
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I suspect the problem is in the carb or you developed a vacuum leak so check all vacuum lines. If the timing isn't stable that too can affect idle speed. If you have a timing light you can hook it up to see if the timing is jumping around while it's surging. Try it with and without the vacuum line connected to the distributor. If you have a vacuum leak that might also be affecting the vacuum advance up and down.
 
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