Horrible gas mileage
10-15-2012, 01:11 PM
#1
Horrible gas mileage
Ok, I just topped off my gas tank and drove about 86 miles round trip to see a guy who specializes in aligning mustangs that are lowered. Upon returning home, I notice my fuel gauge is just under half a tank. This just don't seem right since I made the same trip a couple weeks ago and only used 1/4 of a tank of gas. So I went from 1/4 of a tank to under 1/2 tank in a span of a few weeks. Within the last year, I have replaced my sparkplugs, front 02 sensors and the air filter so all those are basically new and my CEL is not on. ALso, there is no smell of fuel outside of my car so it's not leaking and the car is running good. Do any of you guys have any ideas on whats going on or if I need to replace something? Thanks.
10-15-2012, 02:49 PM
#3
Still using the same gas I have used for a while now. And I don't drive it hard unless im at the track and I haven't been there for a couple months now.
10-15-2012, 03:34 PM
#4
Wouldn't hurt to change PCV and get some MAF sensor cleaner and clean your MAF. Just saying. My PCV was shot and I was losing around 4 mpg. Don't seem like a lot until you sit and watch that needle drop. PCV costs around $5 and the MAF cleaner is around $6-8 at Autozone. Give 'em a shot, cheap and isn't gonna hurt anything. Have you noticed anything different in how it runs??
10-15-2012, 03:36 PM
#5
Wouldn't hurt to change PCV and get some MAF sensor cleaner and clean your MAF. Just saying. My PCV was shot and I was losing around 4 mpg. Don't seem like a lot until you sit and watch that needle drop. PCV costs around $5 and the MAF cleaner is around $6-8 at Autozone. Give 'em a shot, cheap and isn't gonna hurt anything. Have you noticed anything different in how it runs??
Last edited by TRAVIS87; 10-15-2012 at 03:38 PM. Reason: Added info.
10-15-2012, 03:37 PM
#6
10-15-2012, 05:25 PM
#8
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
How would a bad fuel filter cause it to use more fuel?
============================================
OP, failing but not yet dead from O² sensor(s) could be causing it to run rich, and not throw a DTC. As narrowband O² sensor die they still "switch" making the O² monitor happy, however their output voltage drops which tells the PCM the mix is lean. The PCM will, via the short term fuel trims, make it richer until the sensor reports it seems OK--however it will really be quite rich at that point...
============================================
OP, failing but not yet dead from O² sensor(s) could be causing it to run rich, and not throw a DTC. As narrowband O² sensor die they still "switch" making the O² monitor happy, however their output voltage drops which tells the PCM the mix is lean. The PCM will, via the short term fuel trims, make it richer until the sensor reports it seems OK--however it will really be quite rich at that point...
Last edited by cliffyk; 10-15-2012 at 05:28 PM.
10-15-2012, 07:01 PM
#9
How would a bad fuel filter cause it to use more fuel?
============================================
OP, failing but not yet dead from O² sensor(s) could be causing it to run rich, and not throw a DTC. As narrowband O² sensor die they still "switch" making the O² monitor happy, however their output voltage drops which tells the PCM the mix is lean. The PCM will, via the short term fuel trims, make it richer until the sensor reports it seems OK--however it will really be quite rich at that point...
============================================
OP, failing but not yet dead from O² sensor(s) could be causing it to run rich, and not throw a DTC. As narrowband O² sensor die they still "switch" making the O² monitor happy, however their output voltage drops which tells the PCM the mix is lean. The PCM will, via the short term fuel trims, make it richer until the sensor reports it seems OK--however it will really be quite rich at that point...
10-15-2012, 08:02 PM
#10
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
I caution against cleaning MAFs for a couple of reasons, one being that I have only very rarely seen any that needed it. Those being generally ones contaminated by snake oil from improperly cleaned and re-oiled cotton gauze filters, those contaminated because the snake-oil soaked cotton filters don't filter air particularly well, and those contaminated because the paper filter had never been changed and fell apart.
The other reason I do not recommend that they be cleaned (unless of course observation proves the sensor is contaminated) is that the sensor is a relatively delicate thing, if improperly or over-zealously "cleaned" they can be broken.
I have never had to clean one on any vehicle we have owned that had a MAF, this is over at least 300k accumulated miles between my wife and I...
The other reason I do not recommend that they be cleaned (unless of course observation proves the sensor is contaminated) is that the sensor is a relatively delicate thing, if improperly or over-zealously "cleaned" they can be broken.
I have never had to clean one on any vehicle we have owned that had a MAF, this is over at least 300k accumulated miles between my wife and I...