16-18 mpg down to 10-11 in 2 days !
#1
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My 2008 4.7 flex has averaged 17mpg for the last 340k miles. All of the sudden the other night I dropped to 11mpg. Truck runs fine, not rough no check engine light, nada just crappy mileage. Before i drop it off at dodge and have to drive a rental for 2 days any thoughts?
#2
#3
#4
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if an o2 sensor soiled the sheets, it absolutely could drop mileage that far.. the engine will remain in open loop without input from that sensor..
it could also run without tossing a code if everything is still connected, and some sort of signal is coming out of that thing.. those things suck like that..
OP: get a scanner on that thing.. check for codes or pending codes.. if nothing is there, use a scanner that has a raw data function, and look for dead readings.. My guess is you're running in open loop, and very rich as a product of that...
the usual suspects for the PCM not closing loop are (and not limited to):
-o2 sensors
-MAP sensor
-AIT
-thermostat and/or temperature sender/sensor
generally, anything that plays a role in fuel trim...
it could also run without tossing a code if everything is still connected, and some sort of signal is coming out of that thing.. those things suck like that..
OP: get a scanner on that thing.. check for codes or pending codes.. if nothing is there, use a scanner that has a raw data function, and look for dead readings.. My guess is you're running in open loop, and very rich as a product of that...
the usual suspects for the PCM not closing loop are (and not limited to):
-o2 sensors
-MAP sensor
-AIT
-thermostat and/or temperature sender/sensor
generally, anything that plays a role in fuel trim...
#7
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#8
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Interesting thought. Nothing smells hot but ill give it a go since the code scan was a bust,. nothing stored or pending. Just according to the free scanner at the auto parts store.
#9
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You would definatley smell it if your brakes were dragging. Just to be sure you have nothing dragging, coast to around 5mph and put it in neuteral. If you come to a stop abruptly, there is something dragging. Or jack it up and manually turn the wheels. Any drag will kill your mileage. Also, the free scan at the auto store isn't going to tell you much.
#10
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10.78 last tank.... No drag that i can find.
NOW this may be of use. Today I sat in a parking lot with ac on engine running for 15-20 mins. when i put in gear and stepped on gas a HUGE puff of oil burning smoke. Burned off quickly.
The truck does burn a little oil, maybe 1 qy every 1000-1200 miles. Never smokes on startup hot or cold, just some burning under hard acceleration.
NOW this may be of use. Today I sat in a parking lot with ac on engine running for 15-20 mins. when i put in gear and stepped on gas a HUGE puff of oil burning smoke. Burned off quickly.
The truck does burn a little oil, maybe 1 qy every 1000-1200 miles. Never smokes on startup hot or cold, just some burning under hard acceleration.