Join Date: Mar 2017
Location: Lery, Qc
Vehicle: Dakota SLT 2005, Quadcab
Modifications: nothing yet
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Multiple questions / Bad gas milleage
I have a bad gas millage case on my Quad Cab 4.7L Dakota SLT 2WD 2005. I can't say the millage has decreased because it's been like that since i bought it few months back. I am roughly doing 400KMs on a full tank, which would be about 248 miles.
This equals to 20L /100km on highway.
The truck has 150 000 Kilometres, (93 000 miles), NO CHECK ENGINE. The truck runs great and smooth.
I was told Dakotas were not great on gas, but this is pretty bad. From what i read on the internet, i should be able to do 500-550 KMs on a tank. (300-340 Miles)
As i am driving the truck on the highway, i can literally notice the gas needle coming down towards empty.
It is winter time in Canada, temperature is below freezing at the moment.
What i thought / noticed:
-Strong unburned gas smell on startup ( bad EGR valve ? )
-Revving the engine on park also smell like unburned gas. ( i did not notice a leak anywhere )
-I read that a bad clutch fan can cause bad millage too. I can move the fan easy when the engine is stopped & cold. I did not perform other test in that regards.
-I read that bad O2 sensor can happen without a check engine. I don't know if i should try replacing all 4 or just upstream ones.
What i have done :
-changed the engine air filter
-replaced all 8 spark plugs with new NGK 2260
-seafoamed the engine through the brake booster hose and gas tank.
-cleaned the throttle body with a rag
-the truck's brakes are not jammed, tire pressure is good and wheel alignment is excellent.
As you may know, i'm trying to fix this without breaking the bank. I don't want to order and replaces parts that i don't need to.
I don't have a scanner , i am not getting a check engine code either.
I thought of replacing the two O2 sensor upstream ( pre cat ) because i believe they are the only one affecting gas mixture.
Heck, maybe it has multiple issues too.
i ordered 2 DENSO upstream O2 sensor from RockAuto
Last edited by RankinX; 03-20-2017 at 11:22 AM.