when i turn off my car it keeps sputtering

Not to hijack this thread, but would having timing set at 5BTDC or 10BTDC be more likely to cause this? I was running it at 10BTDC and had dieseling. It was also idling at around 850rpm. I changed timing to 5BTDC and also lowered idle to 750rpm. Not sure if what I did was correct, or if I should have left timing at 10. I wasn't getting any pinging at 10.