Q: I have 2001 Ford Taurus with a 3.0 Liter V6 engine. This car will suddenly quit running when I'm driving it. Trying to start it is fruitless for about 10 minutes, and then it will start right up and run until it repeats this same failure, after I've driven it! I took it to my go-to shop. They couldn't find any trouble codes in this car's computer. They've had the car for four days, taken it for two test-drives, and the failure wouldn't repeat itself. Can you help me find the problem? Thank you for looking into the above problem.
A: This is a frustrating situation! Your Taurus is likely losing ignition spark, fuel injector drive (command signals) or fuel pressure. Unless you can establish a reliable pattern (happens after a certain number of minutes of driving, only after purchasing fuel, after a hot re-start, and so on ...) your technician may not be able to duplicate the fault and fix it without some possibly expensive guessing. I have diagnosed numerous cars and learned what it's like to walk home using this method as a tech.
If you don't mind rolling up your sleeves and spending a few bucks, you may be able to narrow the field quite a bit with your own testing during one of the episodes (only if safely off the road!). An electronic ignition spark tester such as the OTC 6589 (resembles a spark plug with a huge gap and attached alligator clip, $20) or Lisle 50850 (adjustable gap spark tester, set it to about 1/2 inch, $8) hooked to one of the spark plug wire ends and clipped to engine metal, can confirm a spark malfunction as the engine is cranked by a helper during an episode. Only a robust ignition system will jump these tools. They'll work as described on most gasoline powered vehicles, including newer ones (wrap a coil-on-plug coil in foil, touching metal, as the tool is used, to look for insulation leaks -- spark won't jump the tool's gap).
Another handy tool is a noid light set such as the Alltrade 940580 ($21), or similar, which contains a half-dozen assorted lights that can be gently attached to the end of an unplugged fuel injector connector. If the light flashes as the engine is cranked, injector drive is occurring. These won't work on newer direct injection systems.
Finally, a fuel pressure gauge such as the OTC 5630 ($33) which fits most 15-year-oldish Ford and GM vehicles, could point out a loss of fuel pressure. Read the directions and safety info before using! Wear eye protection!
Your Taurus employs a waste spark ignition system with three ignition coils, so a faulty coil or ignition control module is unlikely to make it quit (it has three separate coil drivers). I'm thinking you may have a flaky crankshaft position sensor, which would take out both spark and injector drive until it wakes up again. An easy way to check is to look for a tachometer reading while cranking (about 250 rpm, if the Taurus has one). If the tach reads zero, the CKP sensor may be the culprit.
An inexpensive OBD-II scan tool such as the Autel AL519 (a real sweetheart for the $66 price) could also be used to read cranking rpm, in addition to a host of other purposes such as check engine light issues, misfires, and emissions test readiness. I found these tools on Amazon, at the indicated prices. When one looks at the inconvenience of taking a vehicle in repeatedly for an intermittent issue, and the potential for well-meaning but possibly futile labor and parts replacement, spending some money on tools could be a bargain. The scan tool could also make you very popular in your neighborhood!
Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose, Calif. Readers may send him email at email@example.com; he cannot make personal replies.
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