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Rough Idle - Idle voltage Variation

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Rough Idle - Idle voltage Variation

Old 01-07-2019, 11:31 PM
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Rough Idle - Idle voltage Variation


For about 8 months I have had a mild rough idle. Nothing too crazy and no Cel, but every few seconds I feel a shimmy. I have replaced injectors, spark plugs, intake manifold gaskets, cleaned throttles, installed an oil catch can, cleaned O2 sensors, cleaned purge valve, and installed a new interstate battery. The car runs excellent otherwise. There are not any codes stored in the background. While idling I can here a small misfire when the car shakes, sounds like a little pop out the exhaust. I decided to check the voltage on the battery while the car was idling and discovered that the voltage is jumping around some. Even more interesting is that the pops from the exhaust correlate to the dips in voltage. Is this variation while idling normal? Could someone whose not idling rough perform the same test and see if your voltage is stable in comparison to mine? Over a period of 1 minute and 15 seconds the max = 14.26v and the min=13.78v. Thanks in advance.



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Old 01-09-2019, 08:50 AM
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Bump - failing voltage regulator?
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Old 01-09-2019, 12:03 PM
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No codes on obd2, or no codes on Xentry?
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Old 01-09-2019, 12:33 PM
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No codes. About a week ago the car would not start randomly. There was a very strong smell of gas. I let the car sit 15 minutes and turned the key with the gas depressed and it started. I scanned right after this and there was a p0600 serial communication Link. I cleared that code and it hasn't returned. I do not have Xentry.
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Old 01-09-2019, 01:33 PM
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Then you cannot read all the fuel codes.
So yes, you could have non ECU codes that your scanner doesn't pick up.
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Old 01-09-2019, 01:51 PM
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What is the purpose of seeing these fuel codes? I wouldn't have a misfire and a voltage dip if the problem was strictly related to fuel. I'm suspecting that the ignition system is suffering due to the unstable voltage.
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Old 01-09-2019, 04:17 PM
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You wouldn't have a voltage dip and a misfire without having a code.
The problem must be somewhere where your scanner cannot pick up the code.
Once you see the code, this becomes factual, vs opinion of what this might or might not be.

But this is just what I would do, good luck with troubleshooting this.
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Old 01-09-2019, 04:45 PM
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Good point. From my understanding codes are set when limits are reached. So its very possible the issue is borderline a limit and no codes are set. I had the car multiple times at a dealer for other issues and never did they mention issues that could pertain to this. So either they were aware of it and ignored it or Xentry is not showing anything out of the ordinary.
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Old 01-09-2019, 10:04 PM
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Can you post the video? Was the idle RPM changing during the voltage fluctuations? The static pics don't actually help at all.

If there were fuel codes, that could dictate idle RPM changes, that could account for the voltage fluctuations.
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Old 01-10-2019, 11:08 AM
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Bump- Video added to original post
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