HELP! Gas mileage sucks with auto tragic
11-21-2003, 10:03 AM
#1
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HELP! Gas mileage sucks with auto tragic
My 99SE only gets 18 mpg (if I drive fairly conservatively). I got 21 with my 5 speed that had the same mileage on the car. I had hoped to improve the mileage after tune ups and mods, but if anything it seems worse.
MODS: Y pipe, BOMZ CAI with stock resonator. I thought the reduced restriction would improve mileage.
TUNE UP: Replaced plugs, fuel filter
Is it possible to have a bad KS and no codes?
It is definitely not a LACK of power cuz the mods have dramatically improved power....I wish I could get it to the ground, though!
Oh, and it's not that I'm driving it harder, I've experimented with whole tanks of gas and a very light foot and the mpg is as bad or worse than when I bought it.
YES, the awfulmagic owns me!
MODS: Y pipe, BOMZ CAI with stock resonator. I thought the reduced restriction would improve mileage.
TUNE UP: Replaced plugs, fuel filter
Is it possible to have a bad KS and no codes?
It is definitely not a LACK of power cuz the mods have dramatically improved power....I wish I could get it to the ground, though!
Oh, and it's not that I'm driving it harder, I've experimented with whole tanks of gas and a very light foot and the mpg is as bad or worse than when I bought it.
YES, the awfulmagic owns me!
11-21-2003, 10:23 AM
#5
http://forums.maxima.org/showthread.php?t=72447&page=2
almost half way down...try there first. goodluck!
almost half way down...try there first. goodluck!
11-21-2003, 10:48 AM
#6
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Originally Posted by Jepht20
http://forums.maxima.org/showthread.php?t=72447&page=2
almost half way down...try there first. goodluck!
almost half way down...try there first. goodluck!
Thanks! Sadly, I've read that and done "most" of those. The ones I havent done, I suspect will have a lesser effect.
1- air filter - new monster flow on CAI
2- fuel filter - replaced
3- spark plugs - replaced with new plats
4- throttle body - haven't cleaned yet, but I'd be surprised to gain even 1 mpg
5- tp- ?forgot what that one was
6- 02 sensors - no codes stored, expensive way to troubleshoot
7- KS - no codes, 550 ohms exactly
8- fuel system cleaning- could help, but I don't see much improvement in it
Just a guess, but I suspect auto should only suck 1 extra mpg or so, which I could live with. I noted that with half the tank being on the hiway at around 70, mpg is no better.
11-21-2003, 10:49 AM
#7
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Originally Posted by Jepht20
http://forums.maxima.org/showthread.php?t=72447&page=2
almost half way down...try there first. goodluck!
almost half way down...try there first. goodluck!
#5- tire pressure ...checked that, too
Thanks again for thread
11-21-2003, 02:41 PM
#9
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Join Date: Mar 2001
Posts: 408
Mine threw NO codes, but was still bad. It's resistance still measured within spec as well.... and it's 550K ohms, or 550,000 ohms. Take another look at the multiplier on your meter.
What happens, is knock sensors tend to get overly sensitive, and pull the timing back when it's not necessary. This is the reason they don't usually throw a code.
My mileage dropped 4mpg when mine went bad.
$90 + $1 shipping for a genuine Nissan unit on ebay. Make sure to check the wires that lead to it to make sure they aren't bad. Do this by using your ohmeter to make sure they have pretty much zero resistance.
Good Luck!
What happens, is knock sensors tend to get overly sensitive, and pull the timing back when it's not necessary. This is the reason they don't usually throw a code.
My mileage dropped 4mpg when mine went bad.
$90 + $1 shipping for a genuine Nissan unit on ebay. Make sure to check the wires that lead to it to make sure they aren't bad. Do this by using your ohmeter to make sure they have pretty much zero resistance.
Good Luck!
11-21-2003, 07:21 PM
#11
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Originally Posted by n2oMike
Mine threw NO codes, but was still bad. It's resistance still measured within spec as well.... and it's 550K ohms, or 550,000 ohms. Take another look at the multiplier on your meter.
What happens, is knock sensors tend to get overly sensitive, and pull the timing back when it's not necessary. This is the reason they don't usually throw a code.
My mileage dropped 4mpg when mine went bad.
$90 + $1 shipping for a genuine Nissan unit on ebay. Make sure to check the wires that lead to it to make sure they aren't bad. Do this by using your ohmeter to make sure they have pretty much zero resistance.
Good Luck!
What happens, is knock sensors tend to get overly sensitive, and pull the timing back when it's not necessary. This is the reason they don't usually throw a code.
My mileage dropped 4mpg when mine went bad.
$90 + $1 shipping for a genuine Nissan unit on ebay. Make sure to check the wires that lead to it to make sure they aren't bad. Do this by using your ohmeter to make sure they have pretty much zero resistance.
Good Luck!
I usually drive without warming up the car and I think I have a seized/frozen caliper causing a drag 
I'll be happy when I get 18 MPG
11-22-2003, 07:12 AM
#15
Wow, Your guys cars suck! Just kidding guys 
On a serious level though, I get 24 mpg around town and LOVE IT! i have Intake Exhaust, etc etc, and i get 24 mpg around town without a problem...i dont drive like any granny either, You can ask anybody whos ridden with me on the org... All i did to get this kind of milage was knock sensor, new front left, and rear o2 sensors, fuel filter, and tb cleaning!
I run On 93 unleaded, and every time i change the oil, I throw in some injector cleaner... Thats about it!
On a serious level though, I get 24 mpg around town and LOVE IT! i have Intake Exhaust, etc etc, and i get 24 mpg around town without a problem...i dont drive like any granny either, You can ask anybody whos ridden with me on the org... All i did to get this kind of milage was knock sensor, new front left, and rear o2 sensors, fuel filter, and tb cleaning!I run On 93 unleaded, and every time i change the oil, I throw in some injector cleaner... Thats about it!
11-22-2003, 07:12 AM
#16
Senior Member
Join Date: Mar 2001
Posts: 408
Originally Posted by bng4bk
Checked a lot of KS threads. I don't recall seeing anyone whose KS was bad even though there were no codes AND the KS read 550 ohms
My 60 mile commute to work generall provided 26mpg. When the KS went out, it dropped to 22. However, there is only a small amount of 'city' driving here. It's mostly twisty 2-lane and 80mph interstate running.
My car has 'mods' as well, as can be seen below.
Good Luck!
11-22-2003, 08:20 AM
#18
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Join Date: Nov 2000
Posts: 3,883
Originally Posted by bng4bk
Thanks! Sadly, I've read that and done "most" of those. The ones I havent done, I suspect will have a lesser effect.
1- air filter - new monster flow on CAI
2- fuel filter - replaced
3- spark plugs - replaced with new plats
4- throttle body - haven't cleaned yet, but I'd be surprised to gain even 1 mpg
5- tp- ?forgot what that one was
6- 02 sensors - no codes stored, expensive way to troubleshoot
7- KS - no codes, 550 ohms exactly
8- fuel system cleaning- could help, but I don't see much improvement in it
Just a guess, but I suspect auto should only suck 1 extra mpg or so, which I could live with. I noted that with half the tank being on the hiway at around 70, mpg is no better.
1- air filter - new monster flow on CAI
2- fuel filter - replaced
3- spark plugs - replaced with new plats
4- throttle body - haven't cleaned yet, but I'd be surprised to gain even 1 mpg
5- tp- ?forgot what that one was
6- 02 sensors - no codes stored, expensive way to troubleshoot
7- KS - no codes, 550 ohms exactly
8- fuel system cleaning- could help, but I don't see much improvement in it
Just a guess, but I suspect auto should only suck 1 extra mpg or so, which I could live with. I noted that with half the tank being on the hiway at around 70, mpg is no better.
All the fuel stuff is not gonna drop mileage from 27 (auto is rated at 28 mpg) down to 18, again, imho. 18 is fine in city or combined, but totally not good if you're saying it is highway.
11-22-2003, 08:31 AM
#19
Originally Posted by ManualMaxima
does't mod gmake you have more gas mileage? Cause it gives you more power so you do not have to rev as higher to make up for it?
11-24-2003, 07:37 AM
#22
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Well, I installed a resistor (470K+33K+33K+336+536 series) between KS wire lead and ground. I don't see the any change in the performance, at least not the "drives like a new car" performance. I checked the codes beforehand and and a good 0505. It seems its not lying to me, maybe my KS is OK. Damn! I'm probably the only one who is disappointed that his KS is good.
I'm going to clean the TB today. I don't expect to get back 4 mpg, or even 2, by doing that.
I guess my next likely problem could be slow O2 sensors that aren't completely bad, but replacing parts that aren't indicated as bad can be a waste of money.
Any more ideas guys? (I know, buy another 5 speed). I'd have to live in it though if I went that route.
Thanks for the help so far.
I'm going to clean the TB today. I don't expect to get back 4 mpg, or even 2, by doing that.
I guess my next likely problem could be slow O2 sensors that aren't completely bad, but replacing parts that aren't indicated as bad can be a waste of money.
Any more ideas guys? (I know, buy another 5 speed). I'd have to live in it though if I went that route.
Thanks for the help so far.
12-22-2003, 11:36 AM
#23
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Update: Replaced original O2 sensors, which weren't throwing codes. I'm not seeing a big change. Just filled up and it looks like I'm back to 16 mpg from the 14s, so I may have gained a little (or maybe not). I talked to a local mechanic who said the original O2s could go past 100k, so I guess I wasted my money again. Anyone want to buy a very nice, (albeit thirsty) loaded 99SE? I wish I'd kept my stripper SE 5 spd. I was getting 21 mpg on the same drive.
12-22-2003, 11:50 AM
#24
My Auto get 24-26 mpg driving the **** out of it and it has 160,000 miles on it. I got 32 mpg coming back from Florida just this year and the O2 sensors and KS are original - that was cruise control set for 80-85 the whole way and following behind the truck I bought in Florida. The car is pretty much stock.
I don't even know if I could get 16MPG out of it... I'd have to tear it up after every light and dog it to hell and even then I don't know if I could get it that low.
My guess would be O2 sensor. Code or no code... My VG30 is throwing an HO2S intermittently (you have to watch it or it flickers off fast - but I pulled it from memory) and the gas mileage went through the floor. I know yours isn't giving any codes, but that would still be my guess at a culprit. Same thing too - it is down around 14-16 MPG now.
Alright, I just read your last post - I stand corrected.
Hey, I've been wrong before.
I don't even know if I could get 16MPG out of it... I'd have to tear it up after every light and dog it to hell and even then I don't know if I could get it that low.
My guess would be O2 sensor. Code or no code... My VG30 is throwing an HO2S intermittently (you have to watch it or it flickers off fast - but I pulled it from memory) and the gas mileage went through the floor. I know yours isn't giving any codes, but that would still be my guess at a culprit. Same thing too - it is down around 14-16 MPG now.
Alright, I just read your last post - I stand corrected.
Hey, I've been wrong before.
12-22-2003, 05:22 PM
#25
Originally Posted by Entropy
My Auto get 24-26 mpg driving the **** out of it and it has 160,000 miles on it. I got 32 mpg coming back from Florida just this year and the O2 sensors and KS are original - that was cruise control set for 80-85 the whole way and following behind the truck I bought in Florida. The car is pretty much stock.
12-22-2003, 05:26 PM
#26
Originally Posted by bng4bk
Update: Replaced original O2 sensors, which weren't throwing codes. I'm not seeing a big change. Just filled up and it looks like I'm back to 16 mpg from the 14s, so I may have gained a little (or maybe not). I talked to a local mechanic who said the original O2s could go past 100k, so I guess I wasted my money again. Anyone want to buy a very nice, (albeit thirsty) loaded 99SE? I wish I'd kept my stripper SE 5 spd. I was getting 21 mpg on the same drive.
http://www.oxygensensors.com/diagnose.jpg
12-23-2003, 12:49 PM
#27
Originally Posted by JaTaN
You have a y-pipe? I get 14 MPG when I floor it a lot and I get 16-17 MPG when I don't floor it. My O2 sensors are old so they're probably reacting a little slow and I don't think the last owner did much maintainance, so my engine isn't in great shape. I'll probably clean out the engine with Auto-Rx and get a y-pipe later on
Platinum NGKs every 50,000 since new
Mobile 1 5w30 every 4,000 since new
93 Octane or better since new
That is pretty much it.
Just regular maintenance other than that - keeping the fuel filter and that PITA-to-get-to PCV valve changed, that kind of thing.
Might be lucky? I don't know... been like that since I got it and hasn't really varied much. I just filled up yesterday, so I hope to have a more recent number soon.
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