I have a 99' Ford F-250 with the 7.3 turbo diesel. Its got 160,000 miles on it and recently I am having problems with it starting in cold weather. I replaced the glow plug relay and have checked the glow plugs voltage readings and they check fine. It cranks over fine and will start and run rough for about 20 seconds and then will die. If I hold the throttle about half open it will finally run. I have a superchip on it, but am not sure if that is causing any problems. Could it possibly be a bad injector or is there another area I should check with the glow plugs? I would really appreciate some input. Thanks
Paul

Perform the troubleshooting steps in the link below:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-8.html#post1415281

This link discusses diesel fuel and cold weather:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-10.html#post1985158