91 Maxima SE 5spd, 143k miles.

Symptoms include:
*bad fuel economy (18 mpg on highway)
*sluggish acceleration before 2,500 RPMs
*fluctuating idle from 1,200 RPM down to 500 RPM every 2 seconds

 

it may not be either of those i would start with ignition and fuel injectors

 

I have reason to believe its my )2 sensor. the symptoms occur when the engine has been warmed up. Will not fluctuate in idle, or be sluggish when its cold. My O2 sensor comes in tomorrow so I will see if the problem persists.

oh, the car has a new fuel filter, spark plugs, plug wires, and distributor.

 

well let us know if the 02 sensor clears up this problem

 

its your o2 sensor i just changed mine on my 91 se same symptons you described

 

Same symptoms; O2 sensor didn't do it, and I thought for sure it would.

Replacing plugs helped but didn't solve it. I have new coil & primary wire that I'm gonna try next. Otherwise, my shop manual shows it could be anything from air flow sensor to fuel injectors (doubt it) to ECU (or rotor/distrib, but I think mine are ok) or several other things in between. I'm leaning to ECU b/c I'm having a variety of probs that cropped up all of a sudden.

Anyone know have ECU go bad? What are the symptoms (probably varies)?

BTW -- Mine's a 90 SE.

 

Then you don't know nissans.
the 89-91 VG has the most problematic injector of all of the problematic nissan injectors.

 

Well, replaced the O2 sensor tonight at my friend's place. The old one came out with a few taps on the wrench with the hammer. I put anti-seize on the threads and installed new one, then tied it down at the mounting points.

I did tell that the RPMs did not bounce up and down from 800-1200 RPMs, and my fuel economy didn't seem bad coming home either, but will be able to tell once I fill up next week. The car now idles around 600 RPM and it used to run around 800-900 RPM, which was a sign of running rich.

I still have the engine drop to a very low RPM when I put it in neutral to come to a stop, then comes back up again. Anyone know what the problem here could be? Vacuum line perhaps?

Oh, if you order the Bosch sensor, you will have to get a tie strap and bunch up the extra wire you will have after its connected.

 

it might be the knock sensor. If your car has these issues AFTER it warms up it is most likely the knock sensor.

 

I'd try some fuel injector cleaner, it sometimes helps the idle. Otherwise check for dirty TB, vacuum hose leaks, and possibly bad TPS. Maybe have autozone pull some codes?

 

id place bets on the maf, those were the symptoms i had when mine was bad

at least the maf is easy to access so its worth checking out; id swap mafs with another 3rd gen vg and see if it clears the problems

 

So would it be worth it going to the salvage yard and pulling a MAF sensor off a lower mileage maxima? Wouldn't the CEL light come on if the MAF sensor was bad?

To me, it seems like I fixed 75% of the problem I was having, just the rpms dropping too low when I take it out of gear to come to a stop.

 

could just be an old/dirty MAF

when my maf went dead my car ran really and i mean really ****ty to the point where it was easier to drive it with the MAF unplugged but still didnt throw a code or light

 

Curiosity: subs1000w, can one clean a dirty MAF? or does this damage the sensors?

 

Yeah, how do you clean a MAF sensor?