enkrypt3d Posted July 13, 2013 Share Posted July 13, 2013 my pathy has only 156k miles on it - timing belt, water pump service just performed. Cleaned the intake throttle body and seafoamed it which really helped. The engine seems to have great power but this last tank I only got about 180-190 miles out of it which means I'm getting less than 10mpg on a 20 gallon tank... would headers really improve mpg and power too? I'd have to upgrade the cats & cat back system too..... thoughts?? my commute is 8 miles round trip every day so its not a biggie its just the longer trips thats killer. And the engine can spin the wheels on slick concrete in 1st gear..... so it has power just sux at gas mileage ....... Link to comment Share on other sites More sharing options...
Trogdor636 Posted July 13, 2013 Share Posted July 13, 2013 Are you checking gallons at fillup or are you guesstimating? Because my truck will go forever on E. Link to comment Share on other sites More sharing options...
enkrypt3d Posted July 13, 2013 Author Share Posted July 13, 2013 Pretty much - Last time I ran it as empty as I thought I could and I think it had 2 gallons in it... and it ran about 195 miles... is there an idiot light when the gas gets too low? I've never seen it come on if so even with the needle below empty.. still 10-12 mpg is still @!*%e... short of rebuilding the engine which wouldn't be worth it most likely what else can i do? Link to comment Share on other sites More sharing options...
wolkersdorfer2 Posted July 13, 2013 Share Posted July 13, 2013 What kind of mods do you have? Tires etc, and manual or auto? % city/highway? Sent from my iPhone using Tapatalk 2 Link to comment Share on other sites More sharing options...
BikerJared Posted July 13, 2013 Share Posted July 13, 2013 (edited) If you don't trust your gas gauge, when my idiot light comes on, I routinely fill up with 17-18 gallons of gas. I'm at 4500 ft elevation in Utah, and before I installed any mods, I was averaging 18 MPG. I've got headers and new exhaust and I'm barely scraping 22 MPG if I drive nice. What you're describing means you drive like a nut, or there is something wrong with the truck. It could be a number of things, a mechanic will be able to check them all out. If you know what you're doing, I'd at least check spark plugs and compression. That's generally simple to do. Next I'd look at injectors. If you have a Service Engine Soon light (commonly referred to as a CEL or check engine light), get that checked out. I had an O2 sensor die last winter and my MPG went from 18 to 12. The light came on and the code came back that the system was running lean. Actually, the O2 sensor had died and was reporting bad data. Once you've done that, there are knowledgable people here that can help you take the next steps. As a software engineer, what I've described above is the limit of my experience. A good Haynes manual also has some good diagnostic procedures that you could try on your own. Good luck. Edited July 13, 2013 by BikerJared Link to comment Share on other sites More sharing options...
Slartibartfast Posted July 13, 2013 Share Posted July 13, 2013 Mine's got a few more miles on it than yours (168k now) and the worst I've recorded was 14.7 mpg (winter gas, snow, mild hoonage). I measure mileage by the trip odometer and the gas pump since the fuel gauge is hell for accuracy. If you don't have the trip meter or it doesn't work, you could just write down the main odo reading at each fill-up and go from there. I got my idiot light to come on once by continuing to drive it for a few days after it hit E. I don't recommend this, incidentally, because it apparently caused the fuel pump to suck garbage out of the bottom of the tank and gum up. If your mileage really is that bad, check for codes, check the vac lines, check the MAF and O2 sensors (and check for exhaust leaks between the engine and the O2 sensor). I doubt the motor itself is the issue. A good tune-up (cap/rotor/plugs/wires) is probably your best bet here. Mine seemed to pick up some horsepower with a new (roughly stock size) exhaust, but unless yours is leaking, doing an exhaust system to save gas is going to take a really long time to pay for itself in gas savings. Link to comment Share on other sites More sharing options...
gv280z Posted July 13, 2013 Share Posted July 13, 2013 Enkryptd what kind of driving do you do, mixed city / hwy? 180 - 190 In my estimation would be all city driving stop and go traffic. Something is definetly wrong there. Manual or auto? Clean MAF? Over drive turned off? Check your brake pads and calipers to make sure the calipers aren't siezed up and dragging. Check ignition timing and head / cylinder compression. If you have low compression the engine is only getting a small percentage of benefit from combustion, which would waste a lot of fuel, which would probably also mean you either had antifreeze in your oil because of a head that is loosing it's seat against the block, or your engine would be using / burning oil because of bad rings and blow-by. Low compression can also result from dirty valves that don't seat properly because of carbon deposits, which amounts to the combustion chamber allowing fuel / air mixture to escape when being compressed in preparation for the power stroke when the spark plug ignites. As for your header installation, it's not mandatory that you change out everything else. The collector just has to be able to bolt up, it doesn't matter what comes after / behind the collector. The exhaust piping could remain totally stock allowing you to replace pieces of your exhaust one at a time, you don't have to do it all at once. You could have a 2 1/4" exhaust collector bolted on to a flange with a reducer on the other side to go back down to stock, and then at some point go in with a 2 1/4" pipeing and high flow cat that again reduces back down to stock on the other side and so on until finally it's 2 1/4" all the way out the back. Link to comment Share on other sites More sharing options...
gv280z Posted July 13, 2013 Share Posted July 13, 2013 my pathy has only 156k miles on it - timing belt, water pump service just performed. Sorry, just saw this. What was your mileage prior to having the work done? Link to comment Share on other sites More sharing options...
92Path_68CJ Posted July 13, 2013 Share Posted July 13, 2013 (edited) At 233,XXX miles, mine got 18 MPG. It had a valve job done at about 200k miles. Needed a tune up, and had Yakima cross bars on the roof (drag). I'm shocked that your MPG is that low. And yes, I ran mine till it was almost out of gas to calculate. Edited July 13, 2013 by 92Path_68CJ Link to comment Share on other sites More sharing options...
enkrypt3d Posted July 13, 2013 Author Share Posted July 13, 2013 The entire engine has been tuned up - new spark plugs, coils, wires, rotor, distributor cap etc... timing belt, water pump intake manifold gaskets, all oil pan and vale cover gaskets... maybe one thing I need to clean is the PCV & MAF? Those are the only 2 issues.... that or the injectors aren't spraying well. Link to comment Share on other sites More sharing options...
gv280z Posted July 13, 2013 Share Posted July 13, 2013 well that helps a lot to narrow it down at least. Change your pcv valve and get a fuel system service done, spray some cleaner in the MAF, put a bottle of Gunk or something similar and run through the system, and lastly you need that compression check, or ask the tech that did your front end work if they happened to perform one when they were replacing your front seal. Beyond those things it's going to be something periferral, i.e. exhaust, trans / diff fluid / Did someone already say replace your O2 sensor? I need to do that too...what kind of oil are you using? I like Castrol Syntec and Mobile 1 10 w 30, and whatever best quality oil filter Wix or Fram extra tough guard, what ever filters to the highest efficiency percentage and micron. What about your air filter? Get a K&N drop in atleast if you're still using a paper filter, first thing I did when I got my truck. Link to comment Share on other sites More sharing options...
adamzan Posted July 13, 2013 Share Posted July 13, 2013 I would look into your o2 sensor if you haven't. Since you say it has great power I highly doubt compression is an issue. If it was you would be noticing power loss. Link to comment Share on other sites More sharing options...
gv280z Posted July 14, 2013 Share Posted July 14, 2013 Yeah even though it's my argument I tend to agree with you considering the relative youth of his engine at only 156,000 miles old. It's gotta be something though...there is SOMETHING amiss, something tangible. Well, now it looks like we're down to: General drive train issues / Sensor issues or Exhaust. Oh! I just remembered something! Our trucks rear drive shaft ride on a bearing that sits right behind the transfer case, if that bearing is bad / worn, that would put extreme drag on the power transfer to the rear diff, forcing the engine to have to make more power than it normally would, hence gulping the fuel down. What about your fuel filter under the hood? That's an inexpense replacement item that never hurts to look into and pretty easy to do. If your gas is dirty that's no good. Link to comment Share on other sites More sharing options...
enkrypt3d Posted July 14, 2013 Author Share Posted July 14, 2013 I have run seafoam through the fuel and the intake but couldn't find the right vacuum hose for it to be sucked into the intake manifold... I have replaced the fuel filter as well... the only thing I have not replaced is fuel pump or injectors. I may send the injectors off and have them cleaned and balanced but it may be cheaper to replace them. I've also seen a few CEL's that have gone away that were code 33 which is o2 sensor... The CEL went away though so I don't understand why it would come and go w/o me resetting the ECU. I guess I can have that replaced too and clean the MAF / PCV. Link to comment Share on other sites More sharing options...
enkrypt3d Posted July 14, 2013 Author Share Posted July 14, 2013 I have the oem paper air filter its pretty much brand new but dont want an air filter that requires constant oiling which requires too much maintenance. If the K&N doesn't require oiling then I may replace it. Or replace the entire intake altogether. I really want to throw a blower on it but dont have a clue where I could find one haha Link to comment Share on other sites More sharing options...
gv280z Posted July 14, 2013 Share Posted July 14, 2013 I put K&N in everything I got man, both my nissans and my chevy, my old honda I used to have and the Maxima I had before that. You just take it out once in a while, like every 6 - 8 months or so, knock all the loose dirt out against the sidewalk or side of your house, then spray the cleaning solution on it and let it set for a little bit, then spray it out (from inside out, push the dirt back out of the filter, not INTO it) with a garden hose. Let it dry and then spray a light coating of oil onto it, drop it back in. It beats buying a new air filter twice or three times a year and they flow a lot better. After you clean it out you can almost see through it. I always like to put it up to the sunlight and look through it to find anything I might have missed. Link to comment Share on other sites More sharing options...
enkrypt3d Posted July 14, 2013 Author Share Posted July 14, 2013 Yes I had one of those filters you have to oil on my NSX and it was a PITA.... the oil would collect all the dirt and clog up the filter... even with the lightest spraying of it. I got tired of the maintenance and saw minimal gains unless I replace the entire intake. Link to comment Share on other sites More sharing options...
92Path_68CJ Posted July 14, 2013 Share Posted July 14, 2013 K&N wouldn't be bad for the street, unless you live in a dusty area. Link to comment Share on other sites More sharing options...
enkrypt3d Posted July 14, 2013 Author Share Posted July 14, 2013 Yes I do... Los Angeles is extremely dusty. Link to comment Share on other sites More sharing options...
NC95Pathfinder Posted July 14, 2013 Share Posted July 14, 2013 If you're getting a code for the O2 sensor you should replace it. Mine went bad and it made a big difference in mileage. Another thing I found on mine was the vacuum line going to the fuel pressure regulator had come loose, making the regulator act as if it were at full throttle all the time. I'm still only getting about 15 mpg, but that's mostly city driving, better than the 10 mpg I was getting. Link to comment Share on other sites More sharing options...
enkrypt3d Posted July 14, 2013 Author Share Posted July 14, 2013 http://www.carid.com/universal-air-intakes/kn-air-intakes-appollo-series-534642.html anyone seen this? where could I route the hose to get the best cold air? Behind the headlight? Link to comment Share on other sites More sharing options...
Slartibartfast Posted July 14, 2013 Share Posted July 14, 2013 The factory intake pulls air from the wheel well. You're not gonna get much better than that short of a snorkel. I know a few guys here have tried aftermarket cone filters, but the only huge difference I remember hearing about was a whistling noise. Probably better to concentrate on what you know is wrong before throwing other stuff at it. 1 Link to comment Share on other sites More sharing options...
enkrypt3d Posted July 14, 2013 Author Share Posted July 14, 2013 Right but that tubing is very restrictive and has many bends and curves causing loss of flow and turbulence. Replacing the o2 sensor and cleaning maf is easy... or maybe inspecting that rear bearing for the drive shaft...... Link to comment Share on other sites More sharing options...
92Path_68CJ Posted July 14, 2013 Share Posted July 14, 2013 Cut a hole in the hood. No restrictions there. Link to comment Share on other sites More sharing options...
enkrypt3d Posted July 17, 2013 Author Share Posted July 17, 2013 Cut a hole in the hood. No restrictions there. haha no thanks ... I might as well remove the hood as it weighs 200 lbs (probably more like 50 but still) Link to comment Share on other sites More sharing options...
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