I have a Husqvarna 128 ld. I have used it for two seasons with no problems. I just replaced the spark plug with a new one of the exact same brand and model number. I also checked the gap and torque. Now it will not stay running with the new spark plug. I took it out and put the old one back in and it runs fine. I have tried with two new spark plugs and the same thing happens. Any advice would help.