1996 Pontiac Bonneville SE 3.8 bad gas mileage

Tiny
2CP-ARCHIVES
  • MEMBER
  • 1996 PONTIAC BONNEVILLE
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 66,996 MILES
1996 Pontiac Bonneville SE 3.8 mileage: 67,000. In the past month and a half, my mileage has gone from four hundred and fifty miles per whole tank to three hundred to three hundred and fifty per whole tank. I believe it is a fifteen to sixteen gallon tank. At first, I thought it was due to colder weather when I started getting about fifty miles less per tank. But now (mid December) I am suddenly getting one hundred to one hundred and thirty miles less per tank. What can I check for and what are some possible problems that might be causing this? Thanks!
Friday, October 22nd, 2010 AT 10:01 PM

1 Reply

Tiny
2CP-ARCHIVES
  • MEMBER
  • 4,540 POSTS
If a major tune-up has not been done recently, this could be the cause of your problem. Replace the spark plugs, plug wires, fuel and air filters, etc. Also, replace the oxygen sensor. In addition, service the fuel injection system. Clean the carbon deposits from the throttle bore and idle passages. Check the catalytic converter to make sure it is not plugged or restricted.
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Friday, October 22nd, 2010 AT 10:10 PM

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