Hey all-

About a month ago I began to notice that I've been only getting 250-280 miles out of a tank of gas. Normally I get 340-350, and wondering what the hell is going on. It seemed to start when I got the 1320 code, but since then I replaced the dead coil. I resetted the ECU so it can re-learn the parameters, however its been a month now so that should have been enough time. I've done the usual-tire pressure, pcv, throttle body cleaning,oil change, etc.. but to no avail. Driving habits havnt changed, and even with taking it easy I cant break 300 miles out of a tank.
No SES light other then the misfire and and 1320 code, which have been cleared.....
Anyone have any ideas? I've heard of knock sensors and MAF replacement, but dont want to invest in those unless I know for sure.......

Thanks
Brad

 

Oops forgot:
2000 Max SE w/$tillen intake, but otherwise stock...

 

One factor is the winter gas. Its formulated with additives so not as efficient. Another factor is the cold weather. The cold is good for the car but not for mileage (for me personally, the car drives much better when real cold). Plus warm ups are a ***** on the mileage.

 

Seafoam to the rescue......

 

I got the same prob. Once you get 1320, all coils are misfiring usually. I am getting them all replaced. I tried to replace one (code 0302) but nothing changed..

 

The car also has 97k on it...and now that I've thought of this more I probably should replace all the coils. What about timing belt replacement and valve adjustment? I've read on here that this doesnt need to be done until around 150k, but what I'm experiencing now may call for it.
(I didnt think about the oxygenated gas as a factor...interesting)

 

You don't have to worry about a timing belt. We have chains. As for the valve adjustment, you probably don' need that either. For the 3.5 the adjustment is done with shims.

 

Dude, I am getting them coils and NGk spark plugs today $310 for all 12 pieces.. Will let you know how much of the difference its going to make. By the way, I got 100k on my Max.

 

That's what I was going to say.

 

Its just wierd-I've had the car for 5 years now and I cant remember ever it getting such horrible mileage, even in the winter. I forgot to add that I got the code P420 (or 460) which on a scan tool was something like "stage three catalyst....(cant remember the rest). I tried to retrieve this code again to get it exactly but I cleared it when replacing the coil. I'm assuming that since cylinder 5 was misfiring it was dumping raw fuel into the cat, causing the temp to skyrocket, probably damaging it. (Who knows, maybe it also trashed the O2 sensors also, but just below the parameters so it wont show the SES light for them. This may be contributing to my bad mileage.
Two more questions:
How much are O2 sensors and what is the recommended mileage to replace the timing chain?

Thanks again guys, youve been a lot of help
-Brad

 

You probably won't need to replace the timing chain unless you plan on driving the car for the rest of your life. There is no reccomended interval for timing chains replacment that I know of. Sometimes the chain guides and tensioners need replacement though. Only worry about them if you get to the point where they are very noisy.

 

So I just replaced spark plugs and put in new ignition coils.. Car purrs like a kitten now.. Can't beleive those things are so bad and make so much difference. Idles like new now. Drives awesome..

 

300 miles to a 15 gallon fill-up isn't bad (assuming you fill up when the gas light comes on the second time); Nissan only publishes 21 mpg city....that's about what I always get, and only about 24 mpg highway. Granted I don't drive extremely conservatively like they did to get those MPG projections, but 300 isn't bad city driving.

 

whoa whats all this talk about 340 miles per tank im lucky if i get 220 and i got a 68k 2k1 maxima with a cold air intake only is there something woring with mine ?the most i rev up to is like 2 and a half to 3 off a stop

 

I dont think you need to be alarmed. I just got 250 miles out of 14.5 gallons here in alaska when the temp is 0-25 right now. I use 90 octane and the car drives awesome. I only have 22,000 miles on the car and nothing is wrong with it so getting 250 isn't bad even in the winter. I have yet to drive it long distances since the nearest "city" is ANCHORAGE 357 miles south of here.

 

Yeah, the VQ's are gas guzzlers... I've learned that if I keep the rpms under 3k while accelerating helps out alot, the cold winters kills us, 93 octane gas actually helped, keep warn ups to minimal (depending on the temp) effects the mileage... but in the end, our gas mileage sux regardless

15-17mpg city
17-21mpg highway

 

Hard to believe you got 350 miles city driving out of your MAX.....who was towing you? Or was it just a time you remembered getting 350 and it was mostly highway and some city? Be realistic 20 MPG in the city is excellent, PERIOD. The more mods you have the worse your MPG is going to get.

 

Do you think I would start a link and ask all these people if if I wasnt telling the truth? Not to mention wasting all their time.... (Ive got much better ways of spending my time, you know).....Not a flame, but for real I *did* get 340-350 out of a tank, running it down to E (which I know I shouldnt do) and it's annoying cause this car has been so good to me over the past five years and I hope this is not a sign of things to come.
In the spirit of honesty on long trips cruising around 75-80mph I have approached 400.
By the way the SES light came on today and my friend has a scan tool which he's going to hook up tonight. I'll let you all know what it is......

And no I do not drive like a *****, I am proud of the 4 points on my license.....

 

250/14.5= 17.24mpg....not bad if youre running all city in that weather. I live in the DC area so the weather is a little different here but the traffic is horrible and (before this problem) I would get upwards of 300.... What year is your car?

 

220 is bad. Your model year is pretty much identical to mine, and you have the same capacity tank. I would start by resetting the ECU and driving it the same way you do for a week or two so the ECU can adjust itself again. Then fill,drive till its empty, and do the math. Note closely any hesitation or wierd engine performance during that period. Anomolies will usually show up in open loop.
Check the obvious things too- PCV, use 5w30 oil, tire pressure, etc. It sounds like you have the same setup as I do and I never got that low of a mileage.

220/16.5 tank(fill up)=13.3mpg...I know these can guzzle gas but they ARENT suv's.....
Let me know

 

300 in the city? I have a 03 Max Se and I know the cold isnt that good on gas mileage but its only 15 degrees compaired to what it was a month ago at -40. It is all city driving that I do alot of stop and go traffic lights. I cant really try the power right now becuase there is still ice on the road. What is the temp where you live and what gas do you use. I use 90 octane.

 

weird since i have gotten 1-2mpg better in the last month and its been cold here and i have gotten the 1320 code twice. I am waiting to get the code for the individual cylinder which is misfiring b/c of the coil so until then i will enjoy the better mpg during the last month of winter and maybe along the way replace 1 or all 6 coils and my mpg will get even better. Oh...i have never gotten above 19mpg since i bought the car last march.

 

I didnt know the exact code either, however you can "aggravate the condition" by doing the following steps:
Start off the traffic light slow, then upshift prematurely so the motor is under load...this should trigger a solid misfire, and hopefully will send a fault to the ECU on which cylinder....you will know when it happens....stay on the gas during the hesitation, it will eventually light the SES light which will pinpoint the cylinder. Thats what I did, and it saved me repacing all six coils.

Dont do what I did and wait-misfiring dumps raw fuel into the cat which can destroy it along with the O2 sensors....as soon as you get the two codes..the 1320 (which you already have) along with the misfire code (cylinder specific) then you know......replace it as soon as you can....