A high idle speed can be caused by a poor connection at the Throttle Position Sensor (TPS). Connector replacement kits are available from Mazda dealers and possibly some Ford dealers.
Average mileage: 126,166 (61,000–200,000)
Engine affected: 2.5L 4 Cylinder
15 people reported this problem
Engine speed increases, often as high as 3500 rpm, when clutch is depressed. Doesn't happen all the time. Drops back to normal when truck is brought to a stop.
Idle surges to high rpm's? Idle sensor connector at top middle rear of motor gets dust in it. Disconnect, blow out, and tape w/electrical tape to keep dust out. Never had a problem since.
I have a 2000 B2500, with the manual transmission. I had the high idle problem and the poor idle condition. Every once in a while it would run rough and no engine light. I replaced the throttle position sensor,and took apart all the harness connection spots and cleaned them. I also replaced the timing belt, water pump, spark plugs, and the wires. The truck runs perfect now. I don't know witch one of those fixed that problem, but for about 200 dollars in parts and a weekend of working on it, it runs perfect. I get about 2-3 more miles per gallon now also. Its well worth the time to just replace everything listed above and be done with it.