I own a 1999 malibu with a 3.1 that will not start unless I step on the gas while cranking. Also will not stay running unless i stay on the gas. had problem not starting once before about 2 weeks ago and when it did start it was fine until now. put new plugs and wires on and does same thing. will hook up obd code reader tomorrow but was wondering if anyone had any ideas where to start. car has 135,000 miles on it.