Question about 1999 Plymouth Voyager

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SUDDEN LOSS OF MPG AFTER DEAD BATTERY Hello. We have a 1999 Plymouth Voyager. Wonderful vehicle -- well engineered and comfortable. Last year our mileage dropped suddenly from 36 mpg to 24 following someone leaving the ignition on while the car was parked for 2 weeks. BCAA jumped the car, and the mpg tanked from that moment. We have seen 3 different mechanics about the problem, which gradually worsened to 22 mpg highway, sometimes worse. One scoped the computer, and changed the tire size setting. That's when it went from 24 mpg to 22 mpg. Another replaced an O2 sensor, and the mpg immediately jumped to 36 mpg again -- for about 1 week, and it dropped back suddenly to 22. No idea why. Another checked, cleaned and replaced everything he could think of related to mileage, including egr valves, air filters, etc. and got the mpg up to 27-28 for several weeks until cold weather hit and our battery failed, resetting our ScanGauge and dropping the mpg back to 22 highway, which it still is 3 weeks later. What the heck is going on? It sure looks like a computer reset glitch, but nobody has a solution. Thank you.

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    KUSTOMBLACK GUNZ Aug 20, 2017

    Just add this and you'll get it all back!



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When the battery went dead you engine control module lost all learned programming, drive it for a few weeks as normal to restore this and the mileage will be back to normal.

Posted on Mar 04, 2017


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Posted on Jan 02, 2017

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SOURCE: all i need is the mpg, i just bought it, its a 3.0

If all is well, and within reasonable shape & mileage, 25-30 shouldn't be out of reach on highway at normal speeds.

Posted on May 24, 2009

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SOURCE: 1999 plynouth grand voyager was coding egr replace

just because the check engine light is back on, it doesn't necessarily mean it is for the same problem. it could be, but would need to pull codes again to find out what its for. literally hundreds of different codes could turn on check engine light. also, was original code for "insufficient egr flow" or "excessive egr flow"? it makes a difference.

Posted on Feb 21, 2010

Testimonial: "Thanks Jason for your help it was very helpful Thanks Brian"

  • 2 Answers

SOURCE: 97 grand voyager, temporary loss of power

cam position sensor-had same problem

Posted on Apr 11, 2010

Testimonial: "Thanks for the suggestion. Voltage and ground for the camshaft position sensor check good. will check it out further."

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