You never mentioned it, but did you change your air filter? Also, did you change your transmission fluid and gear oil? <-- Anything to reduce mechanical resistance would help.
Yup, did that too, replace a spanking new K&N air filter and cleaned the MAF sensor. Changed the transmission fluid with Amsoil Full Synthetic transmission oil. Gear oil? Not yet, but I tested the oil and it is still in good condition.
Quote:
Originally Posted by dave11
SENIOR CITIZEN ABUSE! I am 68 and am getting 16MPG in mixed driving. I only have about 1900 miles on it now. I have a relatively light foot. I did expect a little better mileage, but such is life. I don't try to save on gas. It sounds as if something broke that you haven't found yet.
Definitely something broke and I haven't found yet. I'm trying to replace stuff as budget allows. I hate to replace things while they are not broken. The most expensive items I replaced were the two O2 sensors and the air-fuel ratio sensors. Here and there, it already cost me nearly $2000 to "test" if it was the problem. None found.
__________________ '07 Frontier SE CC Storm Gray: Polk Audio 6X9 front, 6 1/2 rear, 1" in-dash tweeter, Kenwood DDX-6019 HU, Mcintosh MC431 amp for speakers, Punch 600W 4 channel amp for tweeters, MTX Thunderform under-seat 10". Rearview mirror etched with V1 conceal, Injen CAI, Acura TL HID projector Retrofit headlight, ScanGauge w/BlendMount, PRG 2" front, 1.5" rear.
Last edited by XPBQN; 01-14-2013 at 11:43 AM.
Reason: Automerged Doublepost
My MPG dropped off at around 90K it seems when I changed my battery. I know that resets the ECU , but seems I driven long enough to get everything back in sync. Still need to try a different filter ,and clean the MAFS.
__________________
My family is my life, and my life is my family.
2008 Frontier SE 4x4 Auto V6 Crew 91K
35" isn't that much of a tire size jump, but are you going by computer or by odometer? Are you adjusting for tire size on the odometer?
Also, I notice it more on my gen 1, if I drive "like an old person" my fuel mileage drops. I get the same hand calculated mileage if I drive 55 or 75. Just gotta run the engine the way it wants to run.
I dont know if Houston uses winter gas, we use it in Oklahoma and fuel mileage drops a bit. Also, when I have to go to houston, I fill up north of Kingwood and that will usually get me thru Houston and back out. If I fuel up in Houston with the ethanol fuel, I take a hit in mileage.
Have you had the FUEL PRESSURE checked yet? A weak fuel pump or a blocked filter can cause poor milage as the injectors don't have enough pressure to properly atomize the fuel with the air in the cylinders...causing a poor/rich burn creating less power,also therefor causing the driver to use more pedal unkowingly to get that same power...all leading to worse milage.
You said you replaced your thermostat...Did you replace it with a stock one and is the temperature guage reading where it always has read? I asked cause the colder a engine is running genurally the richer the ECM will run the engine until at normal temperature.
Anyways there's my two thoughts. Good Luck to you.
What tires? If you had them installed around 15k and your mileage dips around 50k they might be at the end of their life..
I would be interested to see what your AFR is. I get an avg of 15 MPG right now with about 85% city (stop and go under 35MPH) and 150% highway (50-60MPH). The best live mileage my bullydog has recorded was last night at 29MPG before correcting for tire size. Should be more like 30 after correcting. But that is on a flat, straight road going 33 (so the TC locks in 4th) with no stops.
What I would be most concerned about is where you said you smell gas, and your plugs are wet.. Were all the plugs wet? or just a few?
Have you had the FUEL PRESSURE checked yet? A weak fuel pump or a blocked filter can cause poor milage as the injectors don't have enough pressure to properly atomize the fuel with the air in the cylinders...causing a poor/rich burn creating less power,also therefor causing the driver to use more pedal unkowingly to get that same power...all leading to worse milage.
You said you replaced your thermostat...Did you replace it with a stock one and is the temperature guage reading where it always has read? I asked cause the colder a engine is running genurally the richer the ECM will run the engine until at normal temperature.
Anyways there's my two thoughts. Good Luck to you.
No, I haven't had my fuel pressure checked yet. About the themostat, I replaced it with the stock one and it reads the same as it read before.
__________________ '07 Frontier SE CC Storm Gray: Polk Audio 6X9 front, 6 1/2 rear, 1" in-dash tweeter, Kenwood DDX-6019 HU, Mcintosh MC431 amp for speakers, Punch 600W 4 channel amp for tweeters, MTX Thunderform under-seat 10". Rearview mirror etched with V1 conceal, Injen CAI, Acura TL HID projector Retrofit headlight, ScanGauge w/BlendMount, PRG 2" front, 1.5" rear.
What tires? If you had them installed around 15k and your mileage dips around 50k they might be at the end of their life..
I would be interested to see what your AFR is. I get an avg of 15 MPG right now with about 85% city (stop and go under 35MPH) and 150% highway (50-60MPH). The best live mileage my bullydog has recorded was last night at 29MPG before correcting for tire size. Should be more like 30 after correcting. But that is on a flat, straight road going 33 (so the TC locks in 4th) with no stops.
What I would be most concerned about is where you said you smell gas, and your plugs are wet.. Were all the plugs wet? or just a few?
About the tires, I changed them already. Now I'm on another set of tires and still the same.
My avg mpg is 13.5 combine city and highway. And I know it's low.
All of my spark plugs are wet. And I only smell gas when I open the intake. It concerns me as well, but when I put everything back together, the smell went away.
__________________ '07 Frontier SE CC Storm Gray: Polk Audio 6X9 front, 6 1/2 rear, 1" in-dash tweeter, Kenwood DDX-6019 HU, Mcintosh MC431 amp for speakers, Punch 600W 4 channel amp for tweeters, MTX Thunderform under-seat 10". Rearview mirror etched with V1 conceal, Injen CAI, Acura TL HID projector Retrofit headlight, ScanGauge w/BlendMount, PRG 2" front, 1.5" rear.
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Bad (sticky) injectors allowing too much gas into cylinders?
I was thinking about that as well. But don't know if I would like to put out more than $600 to see if they are the problem. Unless I take out all the injectors and bring them to a shop. Computer check didn't find out anything.
__________________ '07 Frontier SE CC Storm Gray: Polk Audio 6X9 front, 6 1/2 rear, 1" in-dash tweeter, Kenwood DDX-6019 HU, Mcintosh MC431 amp for speakers, Punch 600W 4 channel amp for tweeters, MTX Thunderform under-seat 10". Rearview mirror etched with V1 conceal, Injen CAI, Acura TL HID projector Retrofit headlight, ScanGauge w/BlendMount, PRG 2" front, 1.5" rear.
Some will call it snake oil, but have you considered a motorvac or terraclean, or similar treatment? I believe when they pump fuel into the rail with their machine, the tool will identify if an injector is bleeding. I personally had good results with motorvac on an older car with high miles. Seafoam helped, but motorvac resulted in smoother idle, easier starting, better acceleration, and ultimately MPG went up to where they were suppose to be. Think I was out $150, which beat me pulling off the intake manifold, removing each injector, and spending $100 to have them cleaned/rebuilt, and me having to reassemble everything. Its not a cure-all, but might be worth looking into.
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Andromeda, Rommie for short
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