emas9420

So, i have a problem with my idle. The car sounds good and the idle is within spec, however, when the car is just sitting at idle, rpms go from 650 to 680 to 630 to 610 to 700 and so on. it does this for about 5 seconds really fast. its really hard to feel the change, however it is felt. i tried logging it with my computer to see what it could be. the mass airflow sensors read about 5 g/s (fluctuates from 4-7 ) at idle which is normal. i did clean them and they always stayed the same.

When i checked the 02 sensors i did find something interesting. when doing the ecu reset i saw my check engine light blinking. i tried seeing what it was and it seemed to me like it was throwing a P0133 code...
Checked the 02 sensors and bank 1 sensor 1 always reads in the .400-.500 v at idle. and bank 2 sensor 1 reads at .800-.900 v at idle.

As far as i know, i always thought these sensors were supposed to go from .100-.800. its weird that one seems to be stuck open and the other stuck lean.

I do have to say that this car has nitrous, and it was tuned to run a little leaner than normal.... but even with that the 02 sensor should read the same and only the short term and long term trims should be affected.

anyone know what could cause this? i was thinking maybe a vacuum leak (which i couldnt find any) or an exhaust leak... but since both have a rich or lean issue im not sure.

i did try unpluging the 02 sensors but nothing changed at all in the car... it ran exactly the same. when i unplug the maf the engine obviously reacts to it but just idles at about 1000 rpm and does the same problem where it starts fluctuating...

Could this be a maf problem or vacuum leak or maybe time for new 02?

Thanks

Z33Garage

iTrader: (3)

Did you check the condition of the spark plugs?

emas9420

I'm going to change them along with my filters soon but would that really cause a weird voltage on my 02? I'm going to upload a few pictures in a bit showing what's going on... But the car doesn't have a misfire that's why I don't think it's the sparks

emas9420

UPDATE:

So I raised the car and tested everything I possibly could.

I unplugged the upstream 02 sensors and the computer read bank 1 straight up as .400 and bank 2 as .900. I thought this was supposed to stay at 0 volts?? Am I wrong?

Also when the car was idling I noticed my downstream 02 sensors were at .250 constantly so I unplugged them and they remained the same at .250...

I checked both maf... At idle they read 2.70 Volts. And when I revved the engine the highest it would go was 3.1... I know for a fact this is wrong because at isle it should be barely 1 volt and it should go up to 4 volts at WOT...

Anyways I went for a drive and I noticed that my upstream 02 were the same as I posted the first time... But my downstream 02 started behaving like the upstream should... The fluctuated from .80 v down to .10 v. This is the way that the upstreams are supposed to behave but the downstream are doing it...

How should the downstream sensors behave???
Shouldn't it be a different wave pattern???

Also my short term fuel for the downstream are always 92% and never change...

I should add I don't have any cats btw...


In these 5 pictures the two left graphs are Bank 1 and 2 sensor 2 voltage and the left is bank 1 and 2 sensor 2 short term fuel trim















these pictures the columns on the left are : left top:bank 1 sensor 1 Left Bottom: Bank 2 sensor 1
on the right top and bottomg are bank 1 and 2 sensor 1 short fuel trim








[IMG]http://imageshack.com/a/img855/6238/cg64.jpg[/IMG



These are all the short term fuel trims.. i feel like the two sensor 2 are cancelling the sensor 1 fuel trims but not sure

Z33Garage

iTrader: (3)

Hmm no idea man, I am still learning this fuel trim thing + voltage signals.
Good job with the diagnosis so far, what application are you using for your readouts?

emas9420

Well what I found now is that my downstream 02's are working and not stuck on .250v anymore. Maybe a bad connection... But they fluctuate like upstreams which I don't think is right... And the mafs are supposed to read .08v at idle and mine read 2.5v ...

But anyways, I'm using my laptop and a program called scanmaster, it's really useful and has pretty much everything you possible need for free without having to buy an actual computer... You do need an obd2 scanner though like an elm

emas9420

Bump??

Z33Garage

iTrader: (3)

Thanks! I will download it when I get home and try it out with my elm obd2 scanner. Do you know what the voltage range for the sensors is supposed to be fluctuating between?

emas9420

Upstreams should go up and down from .200 to .800 (little more/little less)

Z33Garage

iTrader: (3)

so this coincides with lean/rich?

emas9420

Yup

Z33Garage

iTrader: (3)

Thank you sir!

myfirstzcar

A flashing ses light means you have a car that's misfiring. You may also have a sensor going bad, but if there's no code for a bad O2 sensor I would dismiss them for now.
My Titan reads about .3-.5 on B1 S1 and about .7-.9 on B2 S2, but both downstreams are steady at about .250 in closed loop. I have a B1 S1 that's going to need replacement soon, but it still does it's job even though it reads out of range slightly.

emas9420

Thats odd. It is a flashing light but i believe it's for a code. Also, it might be misfiring but only on low rpm. I'm
Gonna change plugs and filter Saturday. But maybe it could be the maf

myfirstzcar

You should read the code.
A flashing mil means misfire.

emas9420

I believe it's a p0133 and it only flashes when I go to the ecu reset thing. It doesn't flash otherwise.

myfirstzcar

It's for a B1 S1 slow response, and is usually fixed by replacing the B1 O2 sensor. It can also be a faulty injector, intake leak, or bad wiring/connection.

emas9420

Yeah I know the causes but I don't want to start throwing parts at the problem. I was preferably looking to see if anyone had a problem like this. I don't think 02 are bad . How would I know if they are bad? How do they react?

myfirstzcar

So check for intake leaks and watch injector pulses for a few minutes. Then compare your B1S1 with the B2S2, B1 should be moving around slower than B2 if the sensor is bad.

emas9420

In the pics I posted I show bank 1 and bank 2 sensor one. They both react the same except bank 1 hovers from .04 to .05 and bank 2 from .07 to .08
Did not find any leaks yet . I'll check injectors but I really doubt that's the problem.