engine won't idle when hot
Thread Starter
Intermediate
Joined: Dec 2005
Posts: 42
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engine won't idle when hot
I have a 69 with a 427 auto. When the car is cold and warm it runs great. However, after running on a hwy and in town for a while it won't idle in gear, I have to keep my foot on the gas. The engine idle is set at 1000 rpm without the choke step and will idle around 600 in gear when it is warm. The timing is set at 8 advance, 32 degrees of dwel and 15in of vacuum, compressions is 145to150 in all cylinders. I thought that the fuel was getting too hot because the inline filter was hot to touch so I moved that, it is now a lot cooler, but still no joy. I suspect the carb (Qjet) but I want to make sure it is the carb before I change it out. Also, when it's hot and you shut it off it diesels. Anyone have any thoughts.
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
There is a small bleed valve on the throttle body that either opens or closes when the carb is hot and that valve may be sticking. It is under a little cover. Sorry thats not any more detailed, but I havn't dealt with that in a long time.
Thread Starter
Intermediate
Joined: Dec 2005
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There car doesnt have AC. I will see if I can find the valve on the carb. When the engine is cool the throttle respons is great but once it warms up the is a hesitation when starting from a light, you have to light pump the pedal to keep it going.
Thread Starter
Intermediate
Joined: Dec 2005
Posts: 42
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SIXFOOTER mentioned that there was an airbleed valve on the carb I'm guessing you mean the Hot Idle Compensator? I was looking for that and the carb doesn't have one. Thanks for the tip. Any idea what the compensator does?
The carb on the car is not an original, somewhere in the cars's life the carb was replaced with a rebuild, close to the same year but not exactly.
The carb on the car is not an original, somewhere in the cars's life the carb was replaced with a rebuild, close to the same year but not exactly.
Instructor
Joined: May 2006
Posts: 203
Likes: 1
From: El Cajon CA
It is very important if your intake manifold is original that the metal shim is between the carb and intake. There should be a gasket, metal shim, and another gasket between the carb and intake. Without the metal shim in place the fuel can boil in the carb once it's running awhile and the car will run like crap.
