ArcticDC5

What are the symptoms of a bad O2 sensor? I talked to a guy at napa auto parts, didn't seem to be the smartest at diagnosing a car. I asked him if my O2 sensor was bad. He asked when my car went through emissions test if it passed, and told him it passed with flying colors. So he said it probably wasn't the problem.

My problem is that I get sh*tty gas mileage, 17mpg on the highway with a 91 SE 5spd. The car is very slow before 2,500 RPMs. I am not sure what the problem is. I used fuel system cleaner, so maybe its a bad injector or 2. Who knows. Can anyone can help me please?

D-sta

iTrader: (6)

I don't know if you can exactly test out an o2 sensor. For bad mileage it can be many things that even a new o2 sensor might not fix. Since its not a bad thing to do to a car, I would start with a full tune-up which includes a new o2 sensor. If that doesn't fix it then I suggest to have the injectors serviced since Nissan is know of having a problem with their injectors. But most of the time its a tune up and that imporves the gas mileage greatly.

usmanasif

I have a question about the tune-up. Since the VE has coils instead of distributor and plug wires, and those coils are $80 each at the dealership, should they be replaced as well?

If not, do I just need the platinum plugs and an O2 sensor for a tune-up? Thanks!

D-sta

iTrader: (6)

Well the coils last a much longer time, they need to be replaced if their resistance is out of spec or if they have cracks in them. I've seen coils with 200k on them without any problems. A full tune up includes for a VE;

-Platinum plugs by NGK $10.00 a piece
-Fuel Filter
-o2 Sensor
-PCV valve
-Air Filter
-Fluids changed, Oil and Tranny (don't have to but I like to do it to make sure everything is lubricated with new stuff).

usmanasif

Thanks D-sta! That's gonna be my spring break mini-project. And I agree with changing fluids during a tune-up.....I too like as many goodies working together to complement each other as possible!

89maxSE

You can test an o2 sensor. Dont ask me how though. Did it in vocational school 2 years ago and didn't pay much attention. Get you an ohmeter and ask around

internetautomar

iTrader: (30)

If the o2 has over 60k on it Replace it.
I sell them BTW

usmanasif

IAM, I just sent you a PM about parts

internetautomar

iTrader: (30)

Got it, I'll run the info on monday.

usmanasif

Aight! Thanks!

ArcticDC5

Well, on top of the bad gas mileage. It seems to be very non-responsive before 2.5K RPMs. When I have to merge into traffic running at 55 mph, I have to literally drop the clutch at 2-2.5K RPMs just so I am not rear ended.

I am not sure what is involved with a tune up, but this was replaced 4k miles ago when I bought it: fuel filter, bosch platinum spark plugs, plug wires, distributor, air filter was clean. What else do they do in a tune-up?

Also, back to my original question. What are symptoms of a bad O2 sensor?

harrymay

bosch plugs are your problem, get some ngk plugs and try them.

put in a new o2, symptoms of a bad o2 can be a bad gas smell when running, funny idling. there maybe more, but thats what mine fixed, it also seemed to help a little mileage wise

bonzelite

iTrader: (2)

running rich is a possible symptom of bad o2. your symptoms seem beyond just mere tune-up fix-all.

sounds like you have fuel delivery problem in general. you may be leaking fuel from a cracked line where it goes into the manifold thing. i had that plus bad injectors. all of that will ruin fuel economy. so i replaced it all: O2, injectors, fuel line (soft line coming off hard line), fuel filter. no more gas smell (i had that), no more cutting out or dropping out of acceleration power. just smooth as silk running. engine is responsive and feels sweet.

i will warn that if you find an injector is bad, try to replace them all at once. it will not be cheap even if you do it yourself.

amaxima

Thanks, this is helpful for newbs like me. Do you, or anyone, know what's the difference for the VG tune-up?

usmanasif

Yeah....VG does not have coils, so you will also need a new distributor cap w/rotor and plug wires. Also have your ignition coil checked when you have the dist. cap taken off....often the connectors on those get oxidized. It is also a good idea to check the gasket on the cap to make sure it isn't letting moisture in.

ArcticDC5

Here is another symptom I am having. If I take the stick shift out of gear to start braking, the RPMs will jump down so low that I see a red light come on and off for a quick instance, almost like it was gonna stall. It did stall once though. It will do this all the time.

bonzelite

iTrader: (2)

hmm. does the car idle this way, too? has your timing been f$cked with by anyone? this sounds more like vacuum advance, TPS, timing problem. the car is either not breathing properly, not getting enough fuel, or not getting spark.