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Discussion Starter · #1 ·
I have a 1992 Trooper SOHC 3.2 L with about 59 K original miles. I have noticed lately that my gas mileage has dropped to about 14.5 MPG around town where is used to be about 17 MPG. My highway mileage had dropped also.

I have changed plugs and wires, pcv valve is good. I have inspected all my vacuum hoses but have found nothing.

I was thinking that maybe the o2 sensor is going bad. I have no check engine light. Engine runs smooth just sucking more gas than usual.

Appreciate any thoughts from anyone.
 

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Any change in tires? Are they properly aired, leaking? Just throwing things out here.. Umm, do you have any junk you're hauling around with you? Change your routes at all? That's not a drastic change so it's probably something minor. How about air filter? Different gas station.
 

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Any gas smell?

I'd check temperature sensor. Tis the season for those going out and the computer might think you're running colder than normal.
 

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Discussion Starter · #4 ·
No gas smell, tires are good, air filter is clean. I forgot to mention earlier, I have noticed a "drop in power' s measured by the seat of my pants. That is why I was leaning toward a vacuum leak.

I have the ISUZU workshop manual bought it off ebay for $15.00, I will see if I can get any codes. I will also check the temp sensor.

Sincerely appreciate all your inputs, thanks again
 

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Has you state mandated the use of ethanol in the gas? That stuff causes a drop in mileage. I went from 17-18 in the city to less than 16 once that junk became standard issue at the pumps. I also noticed a slight loss of power using it instead of pure gasoline.
 

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Discussion Starter · #6 ·
Just the usual no more than 10 percent of ethanol. I just checked for codes none just the normal 12 pause than 12 over and over again.

I will also check to make sure my hubs are disengaged. My shifter is in 2 wheel so i am assuming that it is good to go, however it probably won't to double check.
 

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warrant_ero said:
Just the usual no more than 10 percent of ethanol. I just checked for codes none just the normal 12 pause than 12 over and over again.

I will also check to make sure my hubs are disengaged. My shifter is in 2 wheel so i am assuming that it is good to go, however it probably won't to double check.
That is what I was saying. When they added the 10% ethanol here is when my mileage dropped. There is probably nothing wrong mechanically or electrically with the truck, its the crappy fuel causing the mileage drop. If you're running the low grade, try a tank or two of the higher octane and see if the mileage gets better. I run the 87 usually, but on long trips I run the 93 and my mileage goes back up to what was once normal for the 87.
 

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Here are a couple of articles to back up what I'm saying. Some of the comments make the situation very clear.

http://www.fivecentnickel.com/2006/06/0 ... r-mileage/

http://www.cleanairtrust.org/E85-Gas-Mi ... ption.html About half way down they talk about ethanol in gas.

http://blog.thetruthaboutethanol.org/?p=34

http://www.ehow.com/facts_5611281_gas-e ... oline.html

Its universal across the board. Unless you are driving a newer vehicle with an engine specifically designed for it, mileage and power falls from 10 to 30 percent.
 
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