Sometimes it won"t start on 2002 Ford F-150

about once every week or so. My 2002 F-150 just won't start back up after driving awhile. Give it 30 minutes and it starts fine. Also has a hard miss while accelerating especially around 45 mph. I am suspecting a coil pack this truck only has one

by in Lakeland, FL on March 06, 2009
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1 answer
ANSWER by , March 11, 2009
The only way to verify if you are correct is to check for spark during the time of failure. You would need someone to help you perform the test. You need a spark tester, ( something that is like a spark plug, but it has a larger gap between the electrodes and can be attached to ground with a clip) with the vehicle in the no start condition, disconnect a spark plug wire and hook it up to the spark tester, then clamp the tester to a good engine ground point, have the helper crank the motor over, it should have a bright blue spark jumping the gap,(you should keep your hands away from the tester, spark can easily jump to you and give you a good jolt if you are too close). If the bright spark is present, you may have a crankshaft position sensor that is bad, it can cause the same symptoms as a bad coil since it provides the signal to the ignition module. If spark is not present you have to check for power and ground to the coil pack connector, if power and ground are present, then you may have to replace the coil pack. Before changing parts inspect all the connectors for corrosion,(green oxidation on contact pins) good connector pin fit. Coil packs do not go bad very often, crankshaft position sensors do, but they can both cause your complaint.