im getting v8 mileage on a 2.9l...

mikhail · Post by **mikhail** » Sat May 26, 2007 12:32 pm

When im on the highway in overdrive going 65 and up i can notice the gas gauge going down, not really fast, but it used about a 1/8 tank in less than 10 miles id say. thats alot of gas for a tiny v6 considering the tank is 23 gallons.

ive heard of people on this board going 475miles on one tank so something is wrong, because ive never seen a truck get this bad of mileage. it happens when i floor it on the street too.

I think its when the motor is in the upper rpm range. thats one of the main things i dont like on this truck, it runs out of gear at 85. theres no tach, but i can hear the motor doing 3500+ at 70mph.

i cleaned the o2 sensor since then, i know the real fix is to buy a new one i just did that temporarily. Ive run injector cleaner in it but ive heard the only way to clean the injectors is to rebuild them. Ive run sea foam too. The compression seems fine, it doesnt smoke and the power seems normal for a motor this size

im out of ideas though, i cleaned the throttle body. what controls the fuel mixture? because i think it might be running rich, sometimes when i start it it starts on the first or second crank, way faster than most cars. like its leaving too much fuel in the cylinders..?

anyone have an idea? sorry for the long post

Paul · Post by **Paul** » Sat May 26, 2007 8:08 pm

ok there is a couple of things that affect gas milage that dont start with the motor... one check air pressure in tires, too high an too low can affect milage, also check your locking hubs, if they are locked when in 2 or 4 wheel drive they will affect your gas milage ..... the next thing to do is confirm you dont have a leak in your fuel lines.... change or check air filter if you dont want to change it blow it out with compressed air in a reverse fashion (from opposite side of wire mesh)..... check for vacuum leaks ..... most of those are easy checks and require no mony .... and you should REPLACE the 02 sensor..... i am currently doing an 4.0 motor swap but i know my 2.9 had an aweful miss in high rpms ...... but i averaged 18 to 20 miles to a gallon ....... running with 5 speed and 235/75/R 15 with no lift.....so it was pretty much stack if that helps any with the milage issue ........ try checking milage from fill ups to determine an estimated mpg amount ...... i know alot of people have trouble with guages not reading right ..... you might find its reading in an inadeuate level for whats in the tank ....... personally my guage doesnt work i go off my miles on truck an dfill up every 250 miles to play it safe and never use over 12 gallons to fill up....

Paul · Post by **Paul** » Sat May 26, 2007 8:19 pm

chances are if your motor is running smooth and doesnt have a miss in it then its something in the line of the other things, you should also make sure the truck is not locked in four wheel drive while the hubs are unlocked, as this too can affect gas mileage ....... if the motor has a miss, then check spark plugs and plug wires, you might have a cylinder that isnt firing and this will definatly affect gas mileage! the miss i had in my motor was due to the exhaust manifold ....... it was broken and my problem was created by an exhaust leak causing uneven pressure on exhaust system at the nuber 3 cylinder .... one of the reasons i wanted to do the 4.0 swap in mine ...... plus i had over 205,000 miles on the 2.9 and it had never been rebuilt :laugh: :laugh:

84_4x4 · Post by **84_4x4** » Sat May 26, 2007 9:31 pm

my truck gets 10-14 miles to the gallon no matter what i think the truck is just way to heavy and to bulky for a small v6 motor if you own a bronco ii then expect no power and bad gas mileage

mikhail · Post by **mikhail** » Sun May 27, 2007 9:47 am

i dont think its missing, the motor runs fine, doesnt rock any more than a normal v-style engine.
it makes alot of valve clatter, but i heard thats normal for a 2.9

ill check the vaccum lines, theres only about 2 right for the motor right? i looked at the diagram and theres about 1 or 2 for the gas tank. im gonna change the o2 sensor, just need to get the money.

Paul · Post by **Paul** » Tue May 29, 2007 1:36 am

I have an 1989 Bronco II and i was getting 18 - 20 per gallon under normal driving conditions but your right the power level sucked in it.....

cpubuilder · Post by **cpubuilder** » Mon Jun 04, 2007 11:39 pm

One thing that I think wasen't noted above is the Fuel Filter. A plugged fuel filter can rob gas milage alot. Usually 1 year or 12000 kms (I'm Canadian) umm 5000 miles or so should be changed. My Bronco 2 seemed harsh on gas but mine was the O2.

rockcrawlerbronco2 · Post by **rockcrawlerbronco2** » Thu Jun 07, 2007 8:21 pm

sounds to me like its time for a 5.0 swap.

Paul · Post by **Paul** » Fri Jun 08, 2007 1:55 am

i would have loved to do a 5.0 swap but it was easier for me to come up with the 4.0 with low mileage since i hgad one out in the back yard from an explorer my brother rolled a few years back..... so i knew i was in good shape with that motor...... and for 350.00 for the whole truck and it 4x4 i knew i would eventually swap the front and rear too ....... so i went the best route and bought it from him ...... LOL ......i got it as a steal the way i see it ....... under 70,000 miles and runs like a top still...... lol with extra tranny, 4x4 transfer and front and rear axles...... i had too....

Dreded · Post by **Dreded** » Mon Jun 18, 2007 10:39 am

iv owned several BroncoII and I can tell you that for some reason one day they just decide to burn more fuel I have yet to ever figure it out but I used to get 600km to a tank then all the sudden only 400km and this has happened to several different ones... just do the 5.0Swap your fuel mileage will go up lol with the 5.0L I get 24mpg on the HWY :)

Paul · Post by **Paul** » Mon Jun 18, 2007 8:14 pm

ok i know that the AIT and Oxygen sensor or throttle position sensors, can cause it, :wtf: i also know that mine has increased again, i had the fuel return line come loose at the fuel tank :mad2: ...... its pissed me off too when i realize the money it caused me to lose....

bones101 · Post by **bones101** » Sat Jun 30, 2007 12:57 am

I have a fatty hole in my muffler, not the pipes but the muffler itself. Could that be a cause of bad gas mileage?

Paul · Post by **Paul** » Sat Jun 30, 2007 3:08 pm

i have heard of a loss of back pressure causing a motor to run weak, and if it affects teh pressure at the oxygen sensor it might be able too affect gas mileage, but not really sure

Paul · Post by **Paul** » Fri Jul 13, 2007 2:41 am

personally i think i would crawl under the BII and check the fuel return line to make sure its still connected at the tank, remember your fuel pump pumps more volume than needed to substantiate running the vehicle at high speeds, so a leak there might not be noticeable because of the lines going into the tank on the top side of the tank, but it woud definatly effect fuel milage, TRUST ME ...... It took me a 2 months to figure out that was why mine was getting 13 miles to the gallon on Highway and worse in town with a 4.0 but now its closer to 20.... and it took me tracking the fuel line all the way out to find it ....... I never did see it puddling up or any other indication it was leaking untill i crawled under and traced the line form front to rear in it.

bones101 · Post by **bones101** » Sun Jul 15, 2007 11:21 am

if it was leaking then you must have smelt gas right?