Slashjt Posted May 28, 2010 Share Posted May 28, 2010 (edited) Hi there I have a little problem... after doing full maintenance to my 1995 Nissan Pathfinder VG30E 3.0v6 with 197.000km (122.000 miles) and I'm still getting very bad fuel consumption. Driving like a granmother, i'm getting 10.5 miles to the galon (4.5 kilometers per liter) I have a 2" body lift, 2" suspension lift, 32x11.5 maxxis bighorn tires on steel rims. I hope to get 14mpg but 10.5 it's just CRAZY!!!!! I don't have the check engine on and the gases are fine. any ideas??? PLEASE help me PS: I already saw other topics about this using "search" and I still have doubts... Edited May 28, 2010 by Slashjt Link to comment Share on other sites More sharing options...
jbdevega Posted May 28, 2010 Share Posted May 28, 2010 (edited) did you change the o2 senser? are you manual or auto? have you regeared? i noticed my manual drops 4-6 mpg when i went from 31s to 32's, had to regear to get it back. Edited May 28, 2010 by jbdevega Link to comment Share on other sites More sharing options...
Nismojunky Posted May 28, 2010 Share Posted May 28, 2010 have u ran the codes sometimes a cell light isnt given and there are sensors bad.. second have u changed your o2 sensor? Link to comment Share on other sites More sharing options...
nunya Posted May 29, 2010 Share Posted May 29, 2010 Firstmost, what all do you consider "full maintenance"? Link to comment Share on other sites More sharing options...
Slashjt Posted May 29, 2010 Author Share Posted May 29, 2010 did you change the o2 senser? are you manual or auto? have you regeared? i noticed my manual drops 4-6 mpg when i went from 31s to 32's, had to regear to get it back. have u ran the codes sometimes a cell light isnt given and there are sensors bad.. second have u changed your o2 sensor? I have manual transmition, I went from 235/70/R15 to 32x11.5x15 tires. I didn't re-geared (no need, runs very good) I haven't run codes, because the check engine light is not on (no light, no codes... right?) (and yes, the light works)... And I didn't change the o2 sensor because (and let me know if i'm wrong) when the o2 sensor goes bad, check engine light should turn on, and the gases shouldn't be fine... right? Link to comment Share on other sites More sharing options...
Slashjt Posted May 29, 2010 Author Share Posted May 29, 2010 Firstmost, what all do you consider "full maintenance"? spark plugs, air filter, fuel filter, all oils, thermostat, cleaning MAF and checking other sensors, coolant. Spark wires are fine. Link to comment Share on other sites More sharing options...
nunya Posted May 29, 2010 Share Posted May 29, 2010 dizzy cap and rotor good? plugs gapped correctly? Timing correct? (and no light don't necesarrly mean no code, I'd run the check just to make sure. Can't hurt) I get supposedly 9.something MPG on 32s in need of a tune up with an incorrectly working speedometer, for what it's worth as well... Link to comment Share on other sites More sharing options...
Slashjt Posted May 29, 2010 Author Share Posted May 29, 2010 (edited) dizzy cap and rotor good? plugs gapped correctly? Timing correct? (and no light don't necesarrly mean no code, I'd run the check just to make sure. Can't hurt) I get supposedly 9.something MPG on 32s in need of a tune up with an incorrectly working speedometer, for what it's worth as well... dizzy cap and rotor good, plugs good, timing correct. I'll run the check just in case.. My main suspect is the o2 sensor... I checked my speedometer with the GPS and it's exact! no diference... Forgot to mention that I have a leaky exaust... stud problem. Edited May 29, 2010 by Slashjt Link to comment Share on other sites More sharing options...
Nismojunky Posted May 29, 2010 Share Posted May 29, 2010 im putting my money on the o2 they dont always throw a code they may be working but not working correctly Link to comment Share on other sites More sharing options...
Tungsten Posted May 29, 2010 Share Posted May 29, 2010 its either MAF or O2 but most likely O2 as the R50 has a good MAF harness or your cats could be clogged Link to comment Share on other sites More sharing options...
Slashjt Posted May 29, 2010 Author Share Posted May 29, 2010 im putting my money on the o2 they dont always throw a code they may be working but not working correctly how much is an o2 sensor in the states?? Here in chile a good one (no original, but bosch or so) is USD$80 Link to comment Share on other sites More sharing options...
Nismojunky Posted May 29, 2010 Share Posted May 29, 2010 bosch is a good one they run a little leaner 80$ is alright there around that Link to comment Share on other sites More sharing options...
Tungsten Posted May 29, 2010 Share Posted May 29, 2010 $150 for a dealer one Link to comment Share on other sites More sharing options...
Slashjt Posted May 29, 2010 Author Share Posted May 29, 2010 (edited) mmmm.. i'll run the ecu check and let you know. I'll probably change the o2 sensor for a bosch one anyway... EDIT: I ran the ecu check... no codes, all good. Edited May 29, 2010 by Slashjt Link to comment Share on other sites More sharing options...
Indigent Posted May 29, 2010 Share Posted May 29, 2010 Please tell me that you aren't taking your mileage measurements directly from the odometer now that you have bigger tires... You need to do the math to convert how many miles of difference you have between one mile driven on stock tires to your new size and factor that into your math. Link to comment Share on other sites More sharing options...
silverton Posted May 29, 2010 Share Posted May 29, 2010 Unless you changed your speedometer gear, there is no way you're still "dead on" with a gps. With your current setup, stock being 235/70R15's to 32x11.50R15 (292/74R15's) an indicated speed of 52mph(84kph) would be an actual speed of 60mph(96.5kph). When your odometer shows 87miles(140.5km), you will have actually traveled 100miles(160.9km). Your odometer is reading low by 12.7% Hopefully this helps. Link to comment Share on other sites More sharing options...
jbdevega Posted May 29, 2010 Share Posted May 29, 2010 i would regear and change o2 sensor, another trick to see if the o2 senser is bad is to check the idle. if your truck has an erratic idle (idle speed goes up and down) then thats a sign of a bad o2 sensor that wont throw a code. Link to comment Share on other sites More sharing options...
Slashjt Posted May 29, 2010 Author Share Posted May 29, 2010 (edited) Unless you changed your speedometer gear, there is no way you're still "dead on" with a gps. With your current setup, stock being 235/70R15's to 32x11.50R15 (292/74R15's) an indicated speed of 52mph(84kph) would be an actual speed of 60mph(96.5kph). When your odometer shows 87miles(140.5km), you will have actually traveled 100miles(160.9km). Your odometer is reading low by 12.7% Hopefully this helps. Before switching to bigger tires, the speedometer had like 4% error, now the GPS speed and the speedometer are exact... no idea why that happened. I haven't changed the speedometer gear. Thanks for the calculations, I'll check that just in case Regarding the odometer, i'm taking the mesuarement with the digital trip display that the truck has, and as I far as know is reading correctly. i would regear and change o2 sensor, another trick to see if the o2 senser is bad is to check the idle. if your truck has an erratic idle (idle speed goes up and down) then thats a sign of a bad o2 sensor that wont throw a code. How do you re-gear? The truck runs perfect and the idle is smooth. EDIT: I went for a drive, calculating with maps.google.com and... the speedometer is dead on with the gps, BUT! the odometer isn't!!! for every 14 kilometeres, i'm missing almost 2 kilometeres, (so, 14k in my odometer is really 15.8 k aprox, thats 12.8%... just like silverton said..) that improved a little the consumption, but it's still pretty lame. Edited May 29, 2010 by Slashjt Link to comment Share on other sites More sharing options...
Toby Posted May 30, 2010 Share Posted May 30, 2010 regearing means to change the gears in the differential (IIRC). Because you're running bigger tires you need different gears than what were moving your stock 15's. when you do that you'll want to swap in new ones into your front differential. I'd recommend getting gears from a truck that already has 31's. I don't think the 32's would make as much of a difference. But others around here are probably more knowledgable on it. Link to comment Share on other sites More sharing options...
Slashjt Posted May 30, 2010 Author Share Posted May 30, 2010 regearing means to change the gears in the differential (IIRC). Because you're running bigger tires you need different gears than what were moving your stock 15's. when you do that you'll want to swap in new ones into your front differential. I'd recommend getting gears from a truck that already has 31's. I don't think the 32's would make as much of a difference. But others around here are probably more knowledgable on it. that's way out of my budget $$$ ... it's a future mod... and a rear locker. regarding fuel consumption, with the correct calculations I'm getting 12,9 MPG ... that's still kinda low right? Link to comment Share on other sites More sharing options...
ahardb0dy Posted May 31, 2010 Share Posted May 31, 2010 last two times I filled up my 94 I averaged 16.9 & 17.6 MPG that's with worn out 31's and an automatic trans, my O2 sensor has not been changed yet either Link to comment Share on other sites More sharing options...
Toby Posted May 31, 2010 Share Posted May 31, 2010 that's way out of my budget $$$ ... it's a future mod... and a rear locker. regarding fuel consumption, with the correct calculations I'm getting 12,9 MPG ... that's still kinda low right? Then don't complain about poor gas mileage. It's something you should do when you lift and get tires that are that big. Link to comment Share on other sites More sharing options...
Slashjt Posted May 31, 2010 Author Share Posted May 31, 2010 (edited) Then don't complain about poor gas mileage. It's something you should do when you lift and get tires that are that big. I'm just trying to figure out why a friend with the exact same truck (year, specs, bla bla bla) and mods (32's, lift, bla bla bla) is getting 18.8mpg and I'm getting just 12.9mpg I just want to know if it's normal to have that kind of fuel consumption or my truck has something wrong. Edited May 31, 2010 by Slashjt Link to comment Share on other sites More sharing options...
Alkorahil Posted May 31, 2010 Share Posted May 31, 2010 (edited) The computer looks for a flutctuating voltage signal from the O2 sensor. Normal operation is between 0.0 and 1.0V. As long as it is getting a signal within that specified range it will not trigger the CEL on an OBD1 system. The O2 sensor can be bad - constantly giving say 1.0 volts non-stop, and it will make the vehicle run bad since the signal is supposed to vary as the mixture changes so the computer can compensate. Seen this many times. I would also check your vehicle ignition timing a few degrees off will make a difference in milege as well. Edited May 31, 2010 by Alkorahil Link to comment Share on other sites More sharing options...
beastpath Posted May 31, 2010 Share Posted May 31, 2010 Then don't complain about poor gas mileage. It's something you should do when you lift and get tires that are that big. Dude, cut the guy a break. 12 mpg is not normal even with 32s on. Link to comment Share on other sites More sharing options...
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