freyspath Posted March 7, 2011 Share Posted March 7, 2011 Hey guys, Lately i've noticed a big drop in MPG from my NPF. Its an 03 LE 4x4 (I always drive it in 2wd). I fill it up with regular fuel (89 octane) and seem to be getting really bad mpg. So far I am at about 1/2 a tank since I last filled it and have only gotten 68miles! I used to be getting back before I re-bought the car 220miles to a tank. I haven't driven it yet to empty since I bought it, but this is starting to scare me. I sold it to a cousin a year ago with 85k on the clock. Now with 100k and 1 year of time having gone by im starting to worry. Everything work on the truck, no CEL or SES lights, all fluids were flushed last week, and my mechanic told me it was all looking very good for a truck that had 100k on it. Any one know of something causing this?? I dont have a lead foot, nor do I drive my car hard. I generally keep the tach under 2.5k, and dont take off rapidly from stops. Cheers, James Link to comment Share on other sites More sharing options...
Howie Posted March 7, 2011 Share Posted March 7, 2011 Did it just start, or has it been happening gradually? Like, if this were the first time it's happened, then go fill up the tank and see if it is in fact half empty. Hopefully it's just a faulty fuel gauge/sensor. 68 miles on half a tank is about 6.8 miles/gallon, which just doesn't seem possible without throwing a code. Link to comment Share on other sites More sharing options...
Towncivilian Posted March 7, 2011 Share Posted March 7, 2011 Try cleaning your MAF sensor and running some fuel injector cleaner? I've read anecdotes that some fuel injector cleaners can help with a poorly functioning gas gauge sender unit (whatever the thing is called that floats in your gas tank, anyway). Also be sure your SES bulb isn't dead by engaging the parking brake, then setting ignition to ON and checking for it to light up. Link to comment Share on other sites More sharing options...
freyspath Posted March 7, 2011 Author Share Posted March 7, 2011 thanks guys, I will definitely see whats up with it when the tank runs dry. I haven't gone through a tank yet with her since she isn't my daily driver. Ill try putting some fuel injector cleaner in it with the next tank to see if that remedies it. As for my MAF and SES. The SES light works, I see it every time the car is put into the "ON" position. The MAF sensor will be cleaned tomorrow, because I haven't done that since I sold it to my cousin almost a year ago. He drove it all the time on the freeway, like 90% of his driving was freeway. He would fill it on average 2-3 times a week. Yikes! What crossed my mind tonight was the fuel grade. When I bought it, back in December of 2009, I always filled it with 91 "premium" octane gas. I did that all for the year I owned it. When my cousin took it over he only put the 87 regular gas. Now that I have it back, i've been also just using regular 87 octane fuel in it. Mainly because here in SoCal gas prices are off the wall. ($3.89/gal for 87 and $4.05 a gal for premium) Link to comment Share on other sites More sharing options...
adamzan Posted March 8, 2011 Share Posted March 8, 2011 I don't think running regular should get you 7 mpg! Maybe an 02 sensor is starting to get lazy. They don't always set codes. Maybe you could get someone with a scanner that will show the live sensor output and you can tell. Also when was the last time you had a tune up. Link to comment Share on other sites More sharing options...
Towncivilian Posted March 8, 2011 Share Posted March 8, 2011 (edited) Yeah, if you've never had your spark plugs changed now would be a good time to do it. The spark plugs last 105k per the owner's manual and FSM, so they're getting close to the change interval. There's an excellent guide over on NICO if you want to tackle the plugs yourself and save the $255 Nissan would charge. You should probably change the fuel filter if it's also original or not been changed for a while. Edited March 8, 2011 by Towncivilian Link to comment Share on other sites More sharing options...
freyspath Posted March 8, 2011 Author Share Posted March 8, 2011 Hey guys, major UPDATE today. I was driving my PF to the beach just cruising at 35mph (cop was behind me for most of the drive), as I was driving I noticed the SES (Service Engine Soon) light came on. -- For the first time in my life I was happy to get a code haha. I came home, ran the OBD scan and got P0420 - Bank 1. What is that? O2 sensor? Cat? I did a google search "P0420 Nissan Pathfinder" and the bottom line looks to be that 2 O2 sensors need to be replaced, AND the ECU needs to be reflashed. Being that I am over my 80k emissions warranty looks like I get to fork out the cost for the dealer to reflash the ECU... not looking forward to that. Any insights? Cheers, J Link to comment Share on other sites More sharing options...
Phantom01Pathfinder Posted March 8, 2011 Share Posted March 8, 2011 i had the same trouble when got my pathy 4 yrs ago. I got 1 o2 sensor replaced and did the reflash. I did haggle my dealer tho because i was having other issues, so i got parts at cost and free labor to install. Make sure you really need 2 o2 sensors and not just one. get factory o2 sensors, not aftermarket. do the reflash and be on your way . Link to comment Share on other sites More sharing options...
freyspath Posted March 9, 2011 Author Share Posted March 9, 2011 ^^^ Im hoping thats all I need. I went today to my local nissan dealer and one other "JDM" mechanic shop (not affiliated with the nissan dealer). They both said it was my "manifold cat". The CAT on the manifold costs nearly $1200 from Nissan and the corner shop wants $865. Either way im looking at almost a grand to get this working again..... Link to comment Share on other sites More sharing options...
Howie Posted March 9, 2011 Share Posted March 9, 2011 ^^^ Im hoping thats all I need. I went today to my local nissan dealer and one other "JDM" mechanic shop (not affiliated with the nissan dealer). They both said it was my "manifold cat". The CAT on the manifold costs nearly $1200 from Nissan and the corner shop wants $865. Either way im looking at almost a grand to get this working again..... What the hell is a manifold cat? Link to comment Share on other sites More sharing options...
freyspath Posted March 9, 2011 Author Share Posted March 9, 2011 A manifold cat is a catalytic converter basically on the header. From what I learned today, our PF's have 4 cats. Two down stream (before the pipe goes into one) and two upstream right after the headers. Here is a pic below: This picture below isn't the exact same one our car uses, but you get the idea. Link to comment Share on other sites More sharing options...
Howie Posted March 9, 2011 Share Posted March 9, 2011 Okay, I found it in the shop manual. For those of you following along, it's on page EM-11. It's referred to as a Three-Way Catalyst, or TWC. Part number should be: B08A04W100 or B08A04W10A for the right side, or Bank 1, corresponding to your code P0420 (Bank 2, left side would be DTC P0430). That's for an '01 Pathy, but since yours is an '03, you should look it up here: Pathfinder Parts I checked with Everythingnissan.com, where I usually get my parts. They have the best prices I've found. They're charging $673.08 for the TWC (plus shipping). Which is way better than the $1200 your dealer quoted, and even better than the $828.40 MSRP. I hope this helps somewhat. Link to comment Share on other sites More sharing options...
WOT Posted March 9, 2011 Share Posted March 9, 2011 You only have 2 cats. The ones downstream are resonators. Call Nissan to confirm but my qx4 is that way and Id imagine they are the same I would definetely not jump to swapping cats right now. First thing Id do is basic easy maintenance, sorry if you mentioned you did these I skimmed a bit. -6 platinum spark plugs -injector clean -air filter Regular gas isnt going to negatively affect mileage like that either, my Qx4 only sees 87. And I get 250miles to a tank no problem with 120k on the clock. Seafoam is also a good option that I highly recomend. But I suggest you research that indepth before doing it Link to comment Share on other sites More sharing options...
Howie Posted March 9, 2011 Share Posted March 9, 2011 I was surprised too, but if you look at the FSM, there are in fact 4 cats. The manifold cats are UPSTREAM of the big ones, and are almost directly attached to the headers. The resonators are downstream of the rear cats, like you said. Link to comment Share on other sites More sharing options...
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