No spark

5988 Views 5 Replies 4 Participants Last post by Takeda, Mar 20, 2012

countryboy

Discussion Starter · Mar 12, 2012

Hi Guys, I have a 97 f 150 with 4.2 liter. It has been missing really bad. I went to take it to the gas station yesterday and it died about a mile down the road. Would turn over but not fire (no spark), Went back an hour or so later and it fired up but only ran for a minute and died again. Towed it home and checked for spark, No spark. Let it sit overnight and it started again this morning but shaking and missing real bad. Any help as far as the spark then no spark, then spark again?

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Mr Mac

· #2 · Mar 12, 2012

Welcome to the forum.

Sounds like a bad coil to me. Sometimes a coil is bad and there is no doubt, as in it makes no spark at all. But if it's on the way out, but not dead yet, it can make a weak spark that can cause the car to run rough or wrong.

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Takeda

· #3 · Mar 13, 2012

Since it uses a coilpack, which has 3 separate coils, I wouldn't think all 3 coils would go out together intermittently. I would something like the PCM relay, or crankshaft position sensor.

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Mr Mac

· #4 · Mar 13, 2012

While I cannot discount the possibility of those other items I do know that when my '02 had these same symptoms I replaced the coil pack and later determined that the section that controlled firing in cylinders 3 & 4 was causing my issues.

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Arthur37

· #5 · Mar 19, 2012

Has anyone had a jerking issue with the crankshaft position sensor code? I have changed all coils and plugs and the issue is still having a jerking issue.

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Takeda

· #6 · Mar 20, 2012

Mr Mac said:
While I cannot discount the possibility of those other items I do know that when my '02 had these same symptoms I replaced the coil pack and later determined that the section that controlled firing in cylinders 3 & 4 was causing my issues.

Mac, here is a schematic I did for a V-6 coil pack a few years ago. From this, you can see why the plugs in each bank receive opposite polarity spark:

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