Whenever I start the car in mild to cold weather (40-50 degrees) it immediatly goes up to about 2000rpms to warm up and then after about 5 seconds drops down all the way to about 300rpms. Sometimes it will die at that point or it will chug at 300 for a little while and then shoot back up to 2000 and then back to 300. If I mash the gas down a little while it's sitting at 300 it will take a second to respond and then shoot up but then usually go right back to 300. After about 2 minutes the car runs like a champ with no problems. I tried running premium gas for 2 weeks to just see what that did. It only got worse...whenever I would start the car it would die IMMEDIATLY and I had to crank it again. It had a lot greater tendancy to die as well but it ran fine after a minute or 2.
3.8 95 mustang, 110k miles Completely stock except for dual flowmaster system put on..all factory cats and o2 sensors were left intact. In case this means anything I'm getting terrible gas mileage-about 19mpg. Granted I do have a rather heavy foot but that 19mpg is interstate at 85mph.Thanks for any advice!
Jdz