Faulty O2 sensor

DSMboostin15 · 06-28-2008, 03:34 PM

I just finished installing my new O2 sensor and at idle, the voltage cycles like crazy. I knew that they cycled at idle, but I thought that they cycled at a more steady pace. It's almost like the ECU doesn't really know what it wants. Maybe I'm just used to my old O2 sensor, which I think was going out. I've included a copy of a DSMlink log file, so if anyone can give some insight, that would be great.

Also, since I think that my old O2 sensor was going out, will I have to recalibrate my MAF with the new fuel trims.

spyderturbo007 · 07-03-2008, 08:07 AM

Looks normal to me. Old O2 sensors either die or become sluggish in their response time. You're probably just used to your old one.

Also, you need to adjust your airflow sliders. Your AirFlowPerRev at idle is really low.

1992awdlaser · 07-03-2008, 09:09 AM

The o2 sensor activity looks normal to me.

I don't think adjusting the airflow slider is the correct way to fix the g/rev in his case. Based on a current g/rev reading of .18 his 50hz slider would have to be at the +55 mark.

Capture iscposition at idle. If it is not at 30 then adjust the biss screw until it reads 30. Is your valve cover vented? Any boost leaks? Have you verified base timing? All of these will change the g/rev value.

DSMboostin15 · 07-03-2008, 03:26 PM

Thanks for the replies. I figured that I would have to readjust the airflow sliders since I'm running MAFT. Yes I'm venting my valve cover but I'm looking into making a catch can. I haven't done a boost leak test in a while, and I just got a new PCV valve since I'm still rocking a Sonata one that came with my VC. As for adjusting the idle, I was having some problems with my idle staying at ~1200 rpm even though it was set at ~850 rpm. And finally yes, base timing is correct, unless it jumped timing in the past 3 years.

1992awdlaser · 07-03-2008, 03:41 PM

This is the timing I am talking about. Engine Timing

Do a log and capture iscposition. If it is not at 30 then adjust the biss screw until it reads 30.

The valve cover is deffinately a contributing factor for the low g/rev.

DSMboostin15 · 07-03-2008, 04:00 PM

I knew that was the timing you were talking of. It was dead on when I did my timing belt a few years ago. The only way for it to be off is if the tensioner is failing and is literally jumping time. I'd go out to the car right now and check the isc, but I'm feeling lazy and the Simpsons are on.

DSMboostin15 · 07-03-2008, 05:39 PM

Alright, here is a log that I just did. I let the car get to operating temp, then watched the raw ISC setting. So either my ISC is dead/dying or there is not a signal coming from it anymore, because it eventually went to zero. I tried adjusting the BISS but it did not change the raw ISC data, just the idle rpm, like it's supposed to. This car is making me question keeping anymore with every passing day.

EDIT: I just noticed that my WB is reading a constant 18.0:1 even though my O2 voltage is cycling. I've also adjusted my 50 Hz slider in accordance with the STFT and LTFT-Lo. Any advice?

1992awdlaser · 07-03-2008, 06:01 PM

Do that boost leak test before doing anything else.

If you have a timing light I would still check the ignition timing.

You can use the simulate idleswitch feature in dsmlink for the isc.

Your tps needs to be adjusted untill it reads .63 volts.

What kind of fuel pump do you have? Do you know if your fuel presssure is correct? The reason I ask is because your fuel trims are maxed negative. This means the car is getting more fuel than needed and the ecu is trying to compensate by pulling fuel. The ecu can't pull enough fuel though.

DSMboostin15 · 07-03-2008, 06:08 PM

Right now, I'm still on the stock pump and stock regulator, but I'm running 850's. I have the global set to -47% with a dead time of 330 microseconds.

EDIT: Ok, I've adjusted my TPS to 0.63 V.

1992awdlaser · 07-03-2008, 08:02 PM

Quote:

Originally Posted by DSMboostin15

Right now, I'm still on the stock pump and stock regulator, but I'm running 850's. I have the global set to -47% with a dead time of 330 microseconds.

EDIT: Ok, I've adjusted my TPS to 0.63 V.

After any boost leaks are fixed I would drive the car for 10 minutes and then let it ilde for 5 minutes. Then check to see what your lftf's are at. If they are still maxed negative I would put the global to something like -50% and see what the ltft's do.

DSMboostin15 · 07-04-2008, 10:00 AM

Alright, I'll try that. I've fixed 2 already, but the one from the back of the turbo is driving me nuts.