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Old May 18th, 2009, 12:32 PM
GYM's Avatar
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97 SW
Join Date: Jul 2006
Location: West Coast
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O2 Sensor Problem?

Over the past few months, gas mileage has dropped from 12 to 9.5. (97 NAS ST, stock 4.0 gas, 61,000 miles.)

Merging into freeway traffic yesterday, was surprised to see black smoke billowing from the exhaust at full throttle.

No CEL. Truck is not overheating. No rattling coming from cats or muffler and no damage to exhaust system. 60,000 mile service done on schedule. Idles fine. Truck seems to drive fine.

After searching the topic here; I am thinking that the run rich condition and reduced mileage may be one or more faulty 02 sensors.

Any thoughts? Any other possibilities? (ie: VSS?)

Thanks very much.

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Old May 18th, 2009, 12:36 PM
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I have never seen a rover in person
Join Date: Oct 2003
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MAF is the other possibility.

*not legal advice*
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Old August 17th, 2009, 09:16 AM
rover4x4's Avatar
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1995 SW #487/500
Join Date: Sep 2003
Location: The Old North State
Posts: 7,404
I occasionally get some black or grey smoke if I stand in the gas. I am getting 14-15 to the gallon with 255's and I dont pussy foot around. Is this carbon in the top end or fueling issues. 75k with no issues to speak of, the truck is strong. Ive replaced a few things vac advance an o2 sensor because I robbed them to fix my classic.
Poor gas mileage gets you to the best places on earth
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