83,000 miles. The service light came on tonight. The speedometer showed 90 mph on 2000 Lincoln Navigator

I was only going 15 mph. Shifting seemed not good. Added 5 gallons premium fuel. Ran better. Speedometer acted normal. rpm jumped at times. light still on. running rough. made it home. Where do I start to fix this?

by in Covington, LA on November 02, 2012
2 answers
ANSWER by on November 02, 2012
have it scan tested for codes and go from there
ANSWER by on November 02, 2012
start by pulling code(s)