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Jeep Wrangler JK
JK General Discussion
3.6 Pentastar Misfire on Cylinders 1, 3, & 5
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<blockquote data-quote="xackley" data-source="post: 425611" data-attributes="member: 17509"><p>You haven't said if you have OBD2 codes.</p><p>Also have you obtained a scanner</p><p><a href="https://www.amazon.com/gp/product/B011NSX27A/?tag=jkforum-20" target="_blank">https://www.amazon.com/gp/product/B011NSX27A/?tag=jkforum-20</a></p><p></p><p>With very inexpensive software you can monitor the basics of what the PCM(computer) is receiving from sensors and what it is telling the engine to do.</p><p>Start out looking at the fuel trims for Bank1 and the O2 readings for Bank1.</p><p>Warm the engine, it has to be in closed loop, closed loop means it is using the O2 sensors to adjust the fuel/air mixture.</p><p>Long and Short term Fuel trims should be near zero, but may be +-5. More than that and you have a problems</p><p>Sensor 1 bank 1 should fluctuate anywhere between 0 and 1 fairly quickly. </p><p>Sensor 2 bank 1 should not move much and gravitate toward .7</p><p></p><p>I do most of my monitoring on a Windows PC with bluetooth and use software name Car Scanner Pro.</p><p>You can set up screens with half a dozen or so meters and graphs you can observe in real time.</p><p></p><p>There is also a screen that displays all the data it can receive from the PCM, which is handy when you start with a shotgun approach to diagnostics. It takes time and investigation to know what the system names and numbers mean.</p><p></p><p>My jeep had misfire 1,3,5 when switching from open loop to close loop. It sometimes threw a code for O2 sensor voltage High. So the O2 sensor told the computer Bank1 was super rich, the computer not being all that smart, shut off the fuel to the whole passenger side of the engine.</p><p>Turned out that just disconnecting the O2 sensor and plugging it back in restored the sensor's communication with the PCM.</p><p>Don</p></blockquote><p></p>
[QUOTE="xackley, post: 425611, member: 17509"] You haven't said if you have OBD2 codes. Also have you obtained a scanner [URL]https://www.amazon.com/gp/product/B011NSX27A/?tag=jkforum-20[/URL] With very inexpensive software you can monitor the basics of what the PCM(computer) is receiving from sensors and what it is telling the engine to do. Start out looking at the fuel trims for Bank1 and the O2 readings for Bank1. Warm the engine, it has to be in closed loop, closed loop means it is using the O2 sensors to adjust the fuel/air mixture. Long and Short term Fuel trims should be near zero, but may be +-5. More than that and you have a problems Sensor 1 bank 1 should fluctuate anywhere between 0 and 1 fairly quickly. Sensor 2 bank 1 should not move much and gravitate toward .7 I do most of my monitoring on a Windows PC with bluetooth and use software name Car Scanner Pro. You can set up screens with half a dozen or so meters and graphs you can observe in real time. There is also a screen that displays all the data it can receive from the PCM, which is handy when you start with a shotgun approach to diagnostics. It takes time and investigation to know what the system names and numbers mean. My jeep had misfire 1,3,5 when switching from open loop to close loop. It sometimes threw a code for O2 sensor voltage High. So the O2 sensor told the computer Bank1 was super rich, the computer not being all that smart, shut off the fuel to the whole passenger side of the engine. Turned out that just disconnecting the O2 sensor and plugging it back in restored the sensor's communication with the PCM. Don [/QUOTE]
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Jeep Wrangler JK
JK General Discussion
3.6 Pentastar Misfire on Cylinders 1, 3, & 5
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