My little sis has a '98 Malibu with the 3.1L. Check engine light came on and the engine is pulsing at idle (about 100rpm.) She took it to AutoZone to have the code pulled. They said it was 442-small emission leak. Is there any way to diagnose where the leak is backyard mechanic style? I know it can be done with a scan tool or smoke tester, but I don't have either.