Ive had this ever since i bought my car.
I've had tune up's done and all , and jst dont know what the problem is.

I recently had a new engine put in, and i though maybe this would fix it, but still the same problem.

Is a problem with fuel injectors? can they be sending to much gas in to the engine? or maybe sumthing with the fuel pump?

Any ideas would help.

thanks

 

Knock sensor would be my best guess, otherwise check to see if any codes are bring thrown. Could be something different.

 

Just to get the ball rolling Did you do the usually that would increase MPG?

* TB cleaning
* IACV cleaning
* Chage/Clean Air Filter (can really cause bad fuel economy if it hasnt been changed in a while)

Did you check for ghost codes?
If you have a multimeter check you KS to see if its going bad or bad
Check you o2 Sensors too with the multimeter
You may be running rich which would cause heavier fuel consumption.



just curios but how come you had a new engine put in? was it the same year 97? how many miles and cost?

 

replaced the knock sensor about a month ago, have a new k&n filter and no change in mpg.

i also use the highest graded gas available.

MDeezy, when you said i might be running rich , what does that mean, what causes heavier fuel consumtion, since thats what im expecting, because the smell of exhost fumes is very strong

I have no codes comming up, ive checked that also.

The new engine also from 97 was put in since one of the cylinders on my old one wasnt working and 4 other ones had a low compression ratio (about 50-100, when its suppose to be greater than 150), it cost me about 2k, but that included a new right motor mount , and new belts. My old engine had about 107k on it , this one has 80k.

I guess i need to give the TB, IACV cleaning a try. Its just that, when people post getting 300-400 miles per tank , my problem seems to be something more than just a dirty TB and IACV

 

Change both front o2 sensors and your gas mileage should increase.

 

it might increase , but is it whats causing the problem right now.
i was under the impretion that when the O2's go bad, there code that they give out.

 

They slowly go bad, the signal might not be correct, but still within range. Thus it's working, just not really giving the correct oxygen level readings to your ECU. Thats why your not getting a CEL. Incorrect O2 readings will definately give you poor gas mileage and performance. The o2 readings are used to read your a/f ratio. If the readings are off, your ECU may be providing more fuel then really necessary by increasing the injector pulse time.

If your KS has been replaced and your engine is in good running order, all maintenance up to date, the next thing to look at are your o2 sensors.

 

idk, but i had a bad dream tonight taht I had same problem

 

so bad fuel injectors wouldnt cause a bad feul consumtion?

 

running rich mean that the egine is mixing more fuel with air than normal so more fuel is being burned that is needed.

I remember reading about this but cannot remember what is the controller of it, if anyone knows hopefully you can chime in.

cleaning the TB etc, should help out some, but I dont think would be the cause of so a drop in econ.

 

redline much?

 

dont redline much, and its a mix of city and high way driving,, jst eager to fix this due to the rising gas prices

 

Hey, I had my throttle body cleaned at the dealer and they added some fuel injector cleaner in my gas. I brought a full tank of 89 octane into the dealer when they added the fuel injector cleaner. I got about 350 miles per tank and that was all city driving to school. I ran that tank down to about 1/8 or less before I filled up again.

When I filled up I got 91 octane (filled to just about full). It's been half a tank and I have about 120 miles per gallon so far. Now, I'm thinking I'm gonna get around 240 miles per tank on 91. WTF???

 

Full tuneup, equal tire pressures all around, and new oxygen sensors: http://forums.maxima.org/showthread.php?t=289189
http://forums.maxima.org/showpost.ph...6&postcount=39
Check tire pressure and see if you have a knock sensor code. The gas meter is not accurate...

 

i checked thegd, looks like good deal, a question though. Are Both of the front sensors identical? So i just purchase a pair of the same one?

 

I checked for a code and got 0505. Nothing wrong there. And my tire pressure was a little low, so I changed that. Let see if my gas mileage does anything but go down.