poor gas mileage - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 12-19-2009, 12:44 PM   #1
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i have a 1992 pontiac bonneville. and im getting 14-15 mpg. im pretty sure its not supposed to be that low. put fuel injector cleaner in last april. any ideas on why its so bad?
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Old 12-19-2009, 01:07 PM   #2
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Hi Gary when is the last time you gave your motor a tune up? Where are you from?
plugs
wires
O2 sensor
Air filter
Fuel filter
cleaned maf sensor
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Old 12-19-2009, 01:23 PM   #3
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Check all Todd mentioned, but also check your tire pressure, and brakes to make sure they are not hanging up a bit.
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Old 12-19-2009, 01:24 PM   #4
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.....also check all vacuum lines and connections under the hood
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Old 12-19-2009, 01:53 PM   #5
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i live in michigan.
i replaced the plugs wires air filter in april.
i bought a maf sensor form a junkyard in june i never cleaned it. how would you clean it?
O2 sensor and fuel filter no.



DANTHURS what do you mean by the brakes hanging up a bit?
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Old 12-19-2009, 01:58 PM   #6
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https://www.gmforum.com/normal-maintainence-138/cleaning-maf-sensor-278926/

Jack up the car and spin the tires. Do they turn freely? If a caliper is hanging up the brakes will drag and kill your mileage.
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Old 12-19-2009, 01:58 PM   #7
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our tech info has a great write-up on how to clean your maf......EDIT....^^^^^^Dan got here first
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Old 12-19-2009, 02:03 PM   #8
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alright. thanks danthurs. you might know this one too. everytime i press the brakes. they lose pressure and then i have to re pump the brakes. does that mean i need a new brake booster?
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Old 12-19-2009, 07:52 PM   #9
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Sounds more like a master cylinder/hydraulic problem than a booster problem.
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Old 12-19-2009, 07:55 PM   #10
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Try bleeding the brakes first, if that don't work then you will need to rebuild or change the master cylinder.
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