Spark Plugs and Wires
Pontiac Grand Prix
Ford F-150

What could cause a misfire on a 1998 Grand Prix?


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2017-01-16 21:38:39
2017-01-16 21:38:39

There are a variety of possibilities. A misfire is the lack of one or more of the following : Fuel, Spark or Compression in one or more cylinders. A timing belt or chain that has skipped a tooth is a rare but possible reason for lack of compression sequence. More likely is the lack of spark and or fuel. A spark plug, ignition wire, coil pack, module can all cause a misfire. Wet ignition wires can cause this, corroded connections. A faulty fuel injector can cause a misfire. There are more possibilities. Post what you find when you do figure it out. Answer Here is how I do it. The previous post was correct about the compression....if the timing chain is off though, it's off for all cylinders not just the one. This makes timing the least like cause. This generally leaves two other sources...spark and gas. Generally, if it's misfiring on only one cylinder, it is almost always spark. Here is how I figure it out. First thing I do is look under the hood at night. Most of the time, a misfire is caused by a faulty spark plug wire and in the darkness, you can see the spark jumping to some metal object. Of course you can also run your hand along the wires and they will let you know if the spark is leaving the wires, but that's my least favorite way to tell. :-) (Maybe get a person you don't like much to try that method for you!) The next thing I try is to find out which cylinder is misfiring and check to make sure the plug wire is actually delivering a spark to the cylinder. I do this by removing the spark plug and placing it on a metal object to ground the part where the threads on the spark plug are. You can also do this with a short wire with two alligator clips on it. After doing that, start the car and make sure you see a spark jump through the gap on the spark plug. If there is a spark, look toward the fuel injector, if not, then switch plug wires with another cylinder temporarily to make sure the plug wire doesn't have a short. If there is still no spark, the problem is more than likely a coil. You can test the coil for that cylinder with an ohm meter, but I don't know what the ohms are off the top of my head.


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