fuel mixture problem?

[mikhail]

I know the 2.9 is happiest above 2500rpm, ive been driving mine around 1500 and it seems to handle it fine, doesnt accelerate too quick but it can definitely hold the speed, im talking like city driving under 50mph though.

my problem is i think i have fuel problems, cause if i get it anywhere near 3000rpm it uses way more gas than a little v6 should, ive driven 54 miles on $10 worth of gas i put in it last weekend, if i had driven it in the powerband, that wouldve lasted me 2 days at most. it also uses alot of fuel just by giving it 3/4 throttle at any rpm. ive heard a few different things as to what it might be but its not EGR, mine doesnt have that. I think it might be the injectors sticking, but then wouldnt it get bad mileage in the city too? i was about to buy injectors, but i tought id ask on here before i spend $100. i know its normal to get below 20mpg with 33s and 3.45s but im getting better city mpg than i am highway. anyone have any ideas?

 

[AllanD]

Ok, at what rpm and in what gear are you running out on the highway?

I found that even with 3.73's and 235/75 tires I got better mileage
running part throttle in fourth than I could get running in 5th using more throttle.

LOW rpm really does hurt you, particularly if you need to use greater
throttle openings.

The 2.9 is not really "happy as low as 2500rpm, the 2.9 really wants to
be running 2900-3000rpm when cruising steady speed.

a 4.0 is perfectly happy at 2400rpm, a 2.9 isn't

3.45's are your problem.

Hell, I still think that 4.10's might be a touch TOO TALL with 235/75 tires
and I switched to a 4.0!

for 33" tires I'd consider 4.56's to be MINIMUM gearing.

what color is the inside of your tailpipe?

what thermostat are you running?

"Checking for codes" will NOT detect an ECT sensor that's LYING to the computer
and a faulty ECT will make the computer think the engine is "cold" and run it in "cold engine enrichment" all the time which will make your mileage go to hell.

Ditto for a faulty HEGO.

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[mikhail]

when its at 1500 rpm, i hardly have to push the throttle at all, thats the weird thing. i changed my o2 sensor a few months ago (to a bosch), thinking that would be it, i didnt really notice any difference though. the 3.45s are a bit too steep, i think 4.10s would be about right. the 3.45s are ok in 4th gear at 2200rpm but 5th puts it around 1500 and it cant pull the speed at that rpm. the tailpipe is black, looks about normal

 

[AllanD]

Don't discount the possibility that the tack itself is lying to you...

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[mikhail]

its an aftermarket one, mine didnt have one stock. it sounds right though, the rpms and what the tach is reading. i drove it and kept it in the powerband though, and it seems to drive alot smoother and requires a tad less throttle, than when its under 2000. but it still uses alot more gas though... the fuel guage is a little inaccurate though, itll show less if im on a hill or if theres weight shift, say braking or accerlerating