new O2 sensor
new spark plugs
new fuel filter

checked:
MAF sensor
Engine Coolant Temperature sensor
Throttle Position Sensor?
Throttle position switch...

Just ran the ECU self-diagnosis, came out good everytime code 55... This is supposed to cover many parts affiliated with emmissions and fuel system.

What should I check next?

I'm freakin lost, I even took off my 99 5-spokes and put my stock rims+tires back on to see if that could would be of any effect..

Another question, do VEs have 2 O2 sensors???? I read there is supposed to be an upstream and a downstream O2 sensor.. at least its in the 95+ models but how about mine? One of the mechanics I went to, to determine the cause said my car has 2.

Then again, the trouble code from the ECU came up clean.

I need some suggestions or insights, I can't continue to fill up 20$ every 3 days! I've been to Nissan, a rep suggested I use different gas, perhaps 87 or 89 oktane! WTF!!!! and told me at 72$ per hour he can run some sort of a diagnosis but doesn't guarantee it will determine a cause... exactly how he put it...

help pwease!



I searched for it, nothing helpful comes up..
thanks in advance.

 

What about the air filter? I've found that a clean filter restores my mileage on the 4th gen to the tune of 22 mpg dirty to 27 mpg highway clean. Can't seem to ever break 27 anymore, in the old days I could push 30 mpg.

 

Opps, I didn't mention that, yea, I changed the air filter, infact, i changed it last month.. its regular maintanence and I do it like everytime I change oil.

I'm thinking about fuel pressure regulator, fuel lines, exaust, cat, muffler? i dunno..