Rough Idle After Warmup

DJ S

DJ S

Well-known member
I have this strange issue where my tudor will idle beautifully after just a few minutes of running but once it warms up to normal operating temperatures, the idle is extremely rough to the point where you think that the car might die on you. The car however does fine driving down the road and under load but once you stop at a stoplight, the car runs terribly. I also experience a hesitation in throttle response from idle. I'm thinking it might be a cracked intake manifold that is fine when the car is cold because the crack is retracted and not letting a whole lot of air in and when the car warms up, the crack expands allowing more air in creating a lean mixture. What are your thoughts?
 
When it starts running rough spray starting fluid around the manifolds. If the rpm's change you have a leak.
 
DJ S said:
I have this strange issue where my tudor will idle beautifully after just a few minutes of running but once it warms up to normal operating temperatures, the idle is extremely rough to the point where you think that the car might die on you. The car however does fine driving down the road and under load but once you stop at a stoplight, the car runs terribly. I also experience a hesitation in throttle response from idle. I'm thinking it might be a cracked intake manifold that is fine when the car is cold because the crack is retracted and not letting a whole lot of air in and when the car warms up, the crack expands allowing more air in creating a lean mixture. What are your thoughts?
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My experience with cracks is just the opposite. Metal expands and closes the crack.


Sent from my iPhone using Tapatalk
 
Click on "Search" above and enter "carburetor heimlich" under search posts, and find my description of the procedure.

I think your idle jet is plugged, and it can probably be easily cleared. Going down the road uses other jets.

Steve
 
The idle jet can't be plugged because it wouldn't idle at all, hot or cold. GAV on start up is 3/4 of a turn open, after a few minutes I turn it down to 1/4 of a turn. The GAV doesn't effect the idle as it shouldn't.
 
DJ S said:
The idle jet can't be plugged because it wouldn't idle at all, hot or cold. GAV on start up is 3/4 of a turn open, after a few minutes I turn it down to 1/4 of a turn. The GAV doesn't effect the idle as it shouldn't.
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I was guessing that he might have opened the throttle more during warm up, in which case other jets are in play. But, the GAV is certainly something that must be checked.
 
Add to above ideas idle circuit over rich?- not enough air through idle air adjusting screw or idle jet orifice enlarged for some reason?
 
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