Porsche Repair Questions? Ask a Mechanic for Answers ASAP
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The tach signal will drop when the power drop occurs but if it is jumping around or if other gauges and electronics are acting up the same time this issue is occuring here first check and make sure there isnt a loose,damaged or corroded power cable at the battery or leading from the battery itself causing this issue here.Also check at the fuse panels for any loose,damaged or corroded wiring issues.If these are all checked and found to be o.k. let me know so we can continue.
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The only other component that can be common to cause a fault like this here is the electronic ignition switch.I have seen this switch fail on several models in the past before needing replaced to correct faults like this.If you do not locate any cable connection or cable issues at all I would have the switch tested to see if it needs replaced.I would also have the fuel pressure tested to see if this is a low fuel pressure issue with the fuel pump needing replaced as I have seen fuel pump failure quite common before.