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Hi ive got a 2000 Pontiac Bonneville with the 3.8 na. It went on a road trip and out of nowhere it started running rough misfiring popping and banging then will run fine for 5mins ir so then right back to popping and banging. I scanned it and no codes were read. I checked the plugs all 6 are getting spark and 50 psi to the rail. The fuel pressure regulator is about 1000 miles old and didn't have gas coming out of the vacuum. Map and mass airflow were reading normal. The only think i could find is that when the car would act up the crank position sensor would spike weirdly. It would spike to 8k then down to negative rpm??? Weird i thought. Could it be the cps going bad causing the timing of the igniting to be wrong causing the backfires? I have the image of my scan tool and this is what the spikes look like. Thanks the help!
Plot Rectangle Slope Triangle Line
 

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I would check the ignition harness that runs from the module under the coils down to the sensors on cam and crank. There's a ground that can get frayed, and it also had many places that may get pinched for eventual breaks in the wires. You can get an entire replacement harness if you find any issues there, before having to dig all the way in to the crank sensor.
 
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