gruven

I have a 91 Maxima and for the past two weeks it has had a really rough idle. After the car warms up a little, it starts missing bad. Somewhat sporadically, but very often. From idle to the redline. I have replaced the distributor cap, rotor, plugs, and air filter. It smoothed it out, but it's still missing. The car never stalls, but it's just missing. Anyone got any ideas on where to start to figure this one out? Any ideas would be greatly appreciated. Thanks in advance,

DanNY

iTrader: (14)

this one sounds like a O2 sensor. how old is it?? maybe it's a good time to change it. it's located infront of the cat on the Y-pipe...pointed towards the passenger side of the car.
Dan

block

hey dan do you know of any other problems that come along with the o2 sensor being bad besides gas mileage and ruff idle? my car dies every couple of weeks and it has a loss of power sometimes. o2 sensor?

chris92gxe

LOss of power is a big effect with a bad 02 sensor. Once changed you will definitely feel the difference if the previos one is bad. The 02 sensor causes many problems other than bad gas milege.


92GXE, touring wing, 18” racing wheels, Port&Polished intake, custom intake, custom yellow interior, racing seats, back seats taken out and replaced with subs and amps, NOS kit, Suspension tech. Lowering springs, custom grille, soon to be custom painted and have the whole engine rebuilt for big shot NOS and custom SC and tranny converted to 5-speed.

DanNY

iTrader: (14)

does your car run a lot better when it's cold and run poorly when it's hot?
when the engine is cold it doesn't uses the signal from the O2 sensor..so it by passes the signal from the O2 sensor..(open loop i think). so if the O2 is bad it won't matter to the ECU.
when the O2 is heated and the engine is warm it picks up a signal from the O2. if your O2 is lasy or bad your car will run like crap. bad fuel mileage, stalling, black smoke from exhaust, hesitation are all signs of a bad O2. most people will just say "bad MPG = bad O2" which is not the case all the time. best bet is to hook up a ohm meter and measure resistance when the O2 is warm.
good luck.
Dan

DanNY

iTrader: (14)

c'mon chris..he was asking what else besides the power loss and bad MPG.
Dan

Foo90SE

Between what 2 wires? White wire and ground? What should the reading be?
Thanks!

AKAICEBERG

I had the same problem like 2 months ago. The car would just missfire at a stop, but then after a while it would start missfiring during normal driving and highway speeds. This really freaked me out and pissed me off. I noticed that under the hood there was a blue snapping light coming from one of the plug holes. I think it's time you replaced the plug wires, if you haven't already.

Later,
ICE

DanNY

iTrader: (14)

after consulting the bible i found a easier way to check it..
have the car running when u disconnect the O2 sensor does the car run worst or no change? if no change then the O2 is shot.
also u can run a diganostic on the ECU.
BTW it states the voltage should be over 1.0 volts when the car is warm.
Dan

Foo90SE

Over 1.0v??? dayum..mine was .245
ill try the disconnect thing

Foo90SE

Oh...i ran a diagnostics on my ECU yesterday(from what i could understand from the sketchy Haynes instructions) and it flashed the 'normal operation' code...but i saw that there were different modes n such, but it gave no instructions on how to get to different modes or anything.
Ill still try to unplug it and see what happens

Foo90SE

and the car ran the same. Car was at operating temp. and i pulled the plug and it ran exactly the same
Guess i need an 02

Chris Gregg

iTrader: (59)

It seems that everytime someone has a problem, they ask about it and then never get back as to whether what was suggested fixed it! Others who read the threads who have similiar problems don't get any answeres, just a dead end thread. So, let us know for the sake of education!

DanNY

iTrader: (14)

sounds like it to me. let us know..so i can charge you a small fee..heehee j/k
Dan

gruven

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So how did you 'disconnect' the sensor...Mine has three wires coming out of it without a plug on the sensor...Then I can't seem to follow the wires. Do they plug in somewhere in the engine bay? Or do you yank out the entire sensor from the downpipe or something?

Foo90SE

up on the engine crossmember. Look up by the rear motor mount and you'll see it. Slide the thing off of the crossmember, and u can bring it down and disconnect it.

gruven

Nevermind that dumb question...Figured it out. But 1) if you disconnect the sensor when the cars off, does it see the connector as a fault and just stay in "warm up" bypassing the O2 sensor forever. Also, 2) If not the O2 sensor, what else could it be (whats the next step)?

Foo90SE

Well i did it both ways....i disconnected it with the car cold and off. I then ran it till it warmed up...and it stayed running the same. Then i cut the car off, plugged in the 02, fired it back up, unplugged the 02 again with it running and warm. It did nothing on my car.
If that makes no difference...then i would check plug wires. When i got my car it was running kinda rough, and when i replaced all that you said you have replaced it still ran like crap...took a voltmeter and measured the resistance of one of my plug wires and it was 100,000 ohms!(acceptable is 25000). So thats a possiblity too. Sucks that these parts are so expensive..most cars an o2 is 18-30 bucks