I have a 2000 Dakota 4.7 engine (140,000 miles) that for the past week has stalled a couple of times at stop signs. It starts right up again and may not stall again for days. Also sometimes around 40 mph and 60 mph it feels like it stumbles trying to pick up speed. Changed spark plugs no help. The check enging light is not on. Any ideas?

air or fuel filter? had a similar problem on my boss's aunt's car, it was the air filter. go figure.