Ive looked at the stickies and searched but couldnt really find any specific answers so any help would be great. I have a stock 96 auto with 148,000 miles and the car has been really lacking a lot of power and the gas mileage has become worse and worse. i used to get over 300 miles per tank and now average less than 250. The car is fine under normal acceleration, but any more then that, and the car is really lacking in power. The car just doesnt move the way it did maybe even 5000 miles ago. Ive done all the routine stuff to the car like changing all the filters, ngk spark plugs, pcv valve, engine mounts, oil and tranny fluid, changing air intake manifold gaskets, and have even cleaned the trottle body and put in auto rx to no avail. I also scanned for codes but nothing came up. The car barely wants to go to 4k rpms when it used to go to 5 or 6 no problem. Any help would be greatly appreciated because the car just isnt fun to drive anymore and i would probably get burned by cars that would normally get destroyed by a max. Thanks

 

Welcome to my world...

It blows.

 

when all else fails.................change the knock sensor. usually the culprit. i am trying to get a group buy going but i cant start a threat in the buy/sell forums. hopefully someone will have one soon or i will have to order a few from pinnacle.

 

Knock sensor or O2's will cause poor performance.
They might be working (no error codes) but the information they are sending back to the ECU reallys isn't correct. Bad O2 readings will definately cause poor MPG.

 

knock sensor

 

 

You most be new...ebay has them for $64. No need to go anywhere else....

 

You must be new here. The ones on ebay are NOT factory. They are brownbox OEM.

 

I would say it's a knock sensor if you lacking a lot of power, but since you said the car is fine under normal acceleration I don't think it's just a knock sensor.
Regarding you gas mileage: 250miles per tank -> how many % city and % highway ? What gas you buy ? Where you usually drive ? Manhatten ?

I have a similar gas mileage problem. I have a 97 GLE with 190k miles. I get 200 miles per tank (12.5 mpg) driving in Brooklyn, short trips - stop and go, a lot of traffic lights.
I bought my Maxima 6 months ago, and just like you I replaced a lot of things including Knock sensor and all Oxygen sensors and Coolant temp sensor.
After all replacemnts and maintenance I had almost no improvement in gas mileage. I don't drive fast and my auto tranny usually shifts at 2500-3000 rpm.

My car feels powerful under normal acceleration and I never rev over 4k rpm so I don't know if it will go over 4k easily. I never had a maxima before so I don't know how it feels when it's new.

May be the horrible gas mileage is due to prolonged idling in traffic, stop and go driving where you have to accelerate fast and stop every 2 minutes.

 

Ignition boots. Do you notice a miss under accelleration? Unfortunately I can't find the boots alone. You are required to buy the entire coil pack. I have done the knock sensor and it had some effect, but nowhere near the ignition boot problem. The temp sensor is another possible culprit and may not throw codes. My car was running terrible with a bad temp sensor.

Rene

 

Check all the above sensors mentioned, and you may want to try a compression test also.