My car will not turn off. I installed a new ignition switch which did the job for about 2 months, then the problem came back. the car will idle with the ignition switch off(can't really give it any gas or it will backfire) which I think means it's just getting just enough ignition to run. It's a 68 chevelle with a 454 & GM HEI. and yes I am sure it is not dieseling.