Poor MPG

[fastkurve]

Hi guys,

After replacing the plug wires, spark plugs (with correct gap) in order to improve my mpg, I still avg 10 mpg city driving. There is no MIL "ON" and no fault codes recorded.

The engine is a 4.0 SOHC % speed automatic with approx 70K miles on it. The rear end ratio is 3.55. The engine run smooth, from starting , warming up and riding the truck both city or highway, everything run smooth.

I was wondering that perhaps the oxygen sensors are not as efficient as they used to be????

I have AUTOTAP software so I can monitor but I cannot figure if the readings are OK (probably OK since no MIL or code reported) but could be just questionnable........

Any clue??

Fastkurve

 

[Blee1099]

Did you remove the negative battery terminal?

 

[94Blue302GT]

change the oil.
Clean the MAF
Clean the TB

 

[fastkurve]

"YOUR LACK OF SEARCHING DOES NOT MAKE IT AN EMERGENCY"

Blee1099,

I am new to this forum & not use to all the usual ways/preference
of this group. It does not mean that you have to be that "straight"
with such comment.

I did not mention all the things I made or looked for, it would have been boring/anoying to everybody with those details.

I just went to the major things I done or checked.

94Blue302GT,

Thanks for the tips, the oil was changed last week already, only drove the truck for approx 30 miles since then. As for the MAF and TB, I will have a look at those ones but I would had expected a rough idle or erratic engine running with the MAF or TB being dirty.

Fastkurve

 

[Cheesebrat]

thats blee's signature dude. dont freak out.

 

[Axemonkey]

Poor Mileage

I have been having a bit of a mileage issue also. I recently did plugs and wires, always change my oil before 5000 km, just put a new air filter in and cleaned the MAF .. What is a TB?

Thanks

 

[Russ in CT]

TB = ThrottleBody clean it with a can of, you guessed it, ThrottleBody cleaner (autozone, etc).

Have you checked you fuel pressure? You could have a Fuel Pressure Regulator that is supplying too much pressure. I've read on this forum of others with similar low mileage, but engine running fine, that replaced FPR and problem went away (they had high FP readings before they replaced FPR).

 

[Blacksheep Josh]

talk about reviving an old thread. 3 years? damn.

 

[frankofthenorth]

talk about reviving an old thread. 3 years? damn.

I like this old thread, since I have a similar issue with my 2002 Sport Trac 4.0 Auto tranny - I swear my ScanGauge II indicates about 7 mpg!

(its a OBD II error reader/ realtime gauge/trip computer that gets data out of the truck's systems via the OBD II port)

I'm going to check my throttle body, change the oil and see how my MAF sensor looks... I don't really feel like investing in plugwires and plugs at the moment.

 

[rumpledoll]

It could also be a stuck open thermostat that is causing the engine to run in open loop mode.

Rumple

I like this old thread, since I have a similar issue with my 2002 Sport Trac 4.0 Auto tranny - I swear my ScanGauge II indicates about 7 mpg!