stays running with key off

[charger2fast4u]

Having some issues with my 73 challenger after I'm done running it I turn the ignition off  key in off position and the engine stays running but not smooth almost shutting off I have to turn the key on and off acouple times for it to finally shut off I just replaced the ignition switch last summer and it worked no problems until now is it the switch or could it be getting power to the coil another way? I just put a new coil on last week due to another engine problem I'm having   

[John_Kunkel]

If it keeps running rough (knocking and rocking) with the key off it's probably dieseling.

[elacruze]

You probably have the idle speed open too far, allowing the engine to pull in enough mixture to diesel after shutoff.
A lot of carbureted cars have an idle speed solenoid, which is specifically to cure this issue-the solenoid holds idle while running, and disengages to shut the throttle blades completely when you turn the key off.
Check your idle timing, mixture screws, and set the idle speed lower. If all else fails, shut the key off with the trans in gear-don't forget to put it in park after you do so.

[charger2fast4u]

It sounds like its dieseling from what yous say rough idle and knocking what gives it spark though to keep running when the key is off? My 2 areas where I don't know much timing and carb adjusting. Would the idle speed be a screw on the carb that rests against the throttle lever stopping it from closing the butterflies completely? I may start asking some stupid questions but like I said these are 2 areas I haven't messed with to much yet any help running me through the processes is greatly appreciated

[Cooter]

Sounds like a combination of possibly too much timing and or the throttle blades open too far to keep at idle. (Too much screw on base plate of carb). Need to check and adjust timing, then move towardss carb idle adjustment.

[elacruze]

the idle screw will usually be on the driver's side of the carb, and rests against the lever your cable pulls to open the throttle.

Ignition in your case is most likely caused by hot carbon on the piston and head. If too much builds up, it can get red hot in places and cause knocking and high temperatures while running and it will ignite the mixture for some time after the spark plug is shut off. Put a bottle of Marvel Mystery Oil in the next full tank, that will clean off a lot of the carbon as you drive.

If you don't know how to time the engine, find someone who does. If you want to do it yourself, you'll need a timing light and a vacuum gauge-both can be had at your local auto parts or speed shop for not too much cash.

Take your distributor cap off, and make sure that your mechanical advance is not stuck. Rotate the rotor by hand, it should wiggle back and forth about a finger's width with just a little pressure, and should snap right back by itself. Next, make sure the vacuum advance is working by attaching a length of tube to the distributor vacuum pot and sucking on it-you should see the plate with your points or reluctor move around the distributor shaft, and return itself when you release the vacuum.