o2 Sensor going bad?

[Nofear20]

Quite often my A/F gauge will max out rich and stay there, whether I am giving the car gas, or at a dead stop. It will also stutter sometimes when I really get on the throttle. It does not always get stuck on a rich condition, and when it doesn't it seems to work fine, but it always shows that I run rich between shifts (my bov is recirculated). Could this be a bad o2 sensor, or something else?

 

[Gstclipse69]

The o2 should cycle at idle, from lean to rich constantly. My o2 was bad but my car didnt have any of the symptoms that your describing. Have you looked under the hood for an overview. One time my stock intake pipe had a big gash in it causing me to run rich all the time and run like crap.

 

[kenamond]

In closed loop mode (part throttle), the ECU uses the O2 sensor to strive for stoich AFR. The narrowband O2 sensor voltage crosses 0.5v at stoich, so the ECU keeps leaning/richening in an attempt to get the O2v to oscillate around 0.5v. If your A/F gauge is working properly, this tells me that the ECU isn't able to get this behavior out of the O2 sensor. At full throttle, the O2v isn't used anymore, as the ECU goes into open loop mode. It's just taking the airflow from the MAS along with rpm to compute fuel.

If you haven't boost leak tested recently (ever), that's certainly worth doing regardless of this dilema, but I'm not sure what specifically is the cause of the weird A/F reading.

If you boost leak test and fix every leak (so that it holds 20psi and leaks down slower than 1psi every couple seconds), and your problem persists, you may just want to replace the O2 sensor. Mine seemed to start fading at around 80k miles, but I'm sure that varies a lot car-to-car. The sensor costs $47+S&H from oxygensensors.com (I think that's the URL). Just make sure you get the right one. I think I got the Denso one. It's plug-and-play, so to speak. The plug is a bi*** to get at, but it's a pretty straight-forward install. Buy or borrow an O2 sensor socket (slot cut along the side for the wires) and don't forget to use anti-seize on the threads when you put the new one in.

 

[Nofear20]

I have not yet done a boost look test. I am not sure the last time the sensor was replaced the car has 149k miles on it. I am planning on changing the spark plugs, could this change anything?

 

[kenamond]

I guess if some of the plugs aren't firing, then you'd get unburned fuel in the exhaust which would probably show a rich voltage on the O2.

New plugs and wires would be a good idea if you don't know when they were last changed (because you'd now know what's in there and when they were changed ). Get NGK BPR6ES plugs and gap them to 0.028". I used Bosch plug wires, but I hear a lot of folks using other wires. Do some research and pick something that seems to have a good rep and isn't too expensive.

Make yourself a boost leak tester and do a boost leak test. This will probably start a bit of an adventure, as you get to fix the leaks you find. Some are easier than others. Many of the rubber pieces that seal the intake literally turn into a hard, plastic-like material that doesn't seal. But boost leaks can really hurt performance and fuel economy. Anyone who has modded their car knows about boost leak testing and tests regularly (once per oil change or two). The hardest part is that first test when *everything* leaks.

So, change plugs and wires (keep the firing order correct!), gap the plugs correctly (and use the plugs I recommend...$2/ea at NAPA...and don't let them tell you otherwise). Make a boost leak tester and fix the boost leaks. If you can spare the cash, the O2 sensor isn't too bad of an idea.

A lot of the details for any of this is explained here and there on the forum, but if you have questions, just ask.

 

[Nofear20]

Alright thanks a lot for the advice. I already have the NGK plugs gapped to .028, and am thinking of getting some of the Accel spark plug wires. I am going to see if my friend on here (95carboneclipse) will help my non-dsm knowledgeable ass with a boost leak test . Thanks for your advice.

If anyone else has anything else to add please do. Thanks.

 

[kenamond]

Alright thanks a lot for the advice. I already have the NGK plugs gapped to .028, and am thinking of getting some of the Accel spark plug wires. I am going to see if my friend on here (95carboneclipse) will help my non-dsm knowledgeable ass with a boost leak test . Thanks for your advice.

If anyone else has anything else to add please do. Thanks.

We all started somewhere. Fixing boost leaks will make you tear stuff off the car, and you learn by doing. And the more you come to the forums to get answers, the more stuff you learn in the process.

 

[95CarbonEclipse]

How do you think my "non-DSM knowledgable" ass learned anything? It's usually just a matter of getting in there and doing it. Afterwards you realize... "that wasn't that hard at all."

Also, I've learned that because our cars get such a bad rap for being "unreliable" that many people jump to conclusions far too soon thinking that there is a huge problem (or any problem for that matter) when there's really nothing to worry about at all. The best example would be these darn A/F gauges. I remember when I first installed mine (now I realize what a waste of time and money that was) I thought there was something wrong with it because the light would go out when I completely let off the gas. Guess what?? THAT'S NORMAL!

Either way, between me, NoFear20 and the rest of this forum, we'll nip this problem in the butt real quick.

...now if I could only figure out how to make time for all these projects.

 

[Nofear20]

I admit the A/F gauge is stupid but having it show rich all the time shows that somethin is not working right. But yes with your knowledge and my......nothing, we will get the problem figured out .

 

[94cyclone]

1 piece of information that I think gets left out is that usually 2 boost leak testers are required. Especially for that first test when there are so many leaks. One 3" tester for the end of the turbo and one 1.75" tester for the I/C or throttle body. Also, there is a much easier way to make a tester than the one in the vfaq, but that is for another thread.

 

[1gDSM4g63]

I have the same situation as NoFear20; high idle state, stutter and jerking around while I'm driving and eventually dies down.

My wideband keeps of reading lean no matter how I adjust the SAFC. And with the car running 950cc injectors I can tell it's running super rich. I can smell gas fumes coming out of the exhaust and the spark plug has black carbon tips cause by excess gas which burns up.

Besides doing a boost leak test is there are another way to test the o2 sensor to be certain it dead? And it there any other situation I should be looking for?

 

[Nofear20]

To test my o2 sensor, I simply hooked a logger up and monitored the o2 bank 1 voltage. The value should oscillate back and forth. Mine didn't, it sat at around .2 and did nothing. I replaced the o2 sensor which solved that problem, but it did not fix my A/F gauge. My guess is the gauge was bad so I just replaced it with an AEM Uego.

 

[1gDSM4g63]

To test my o2 sensor, I simply hooked a logger up and monitored the o2 bank 1 voltage. The value should oscillate back and forth. Mine didn't, it sat at around .2 and did nothing. I replaced the o2 sensor which solved that problem, but it did not fix my A/F gauge. My guess is the gauge was bad so I just replaced it with an AEM Uego.

Okay, I'll try to do that but have you ever heard of o2 recalibration? I heard that somewhere.

 

[Nofear20]

Nope I am not sure what that is

 

[lazyazzdaddy]

I have the same situation as NoFear20; high idle state, stutter and jerking around while I'm driving and eventually dies down.

My wideband keeps of reading lean no matter how I adjust the SAFC. And with the car running 950cc injectors I can tell it's running super rich. I can smell gas fumes coming out of the exhaust and the spark plug has black carbon tips cause by excess gas which burns up.

Besides doing a boost leak test is there are another way to test the o2 sensor to be certain it dead? And it there any other situation I should be looking for?

I thought I read some where that a safc was only good for injectors under 550cc and any thing over 550cc you would have to use something like dsmlink

 

[1gDSM4g63]

I thought I read some where that a safc was only good for injectors under 550cc and any thing over 550cc you would have to use something like dsmlink

I got a stage 3 Keydiver EPROM chip. It worked alright before.

 

[kenamond]

I got a stage 3 Keydiver EPROM chip. It worked alright before.

Before what? Did you change something or did it just start happening?

If you have a logger, check that the front O2v oscillate above/below 0.5v at idle. If it doesn't, what does it read? Also, check your idle LTFT value and see if it's way above or below 100%.

What do the plug tips look like?

 

[deletrius]

Before what? Did you change something or did it just start happening?

If you have a logger, check that the front O2v oscillate above/below 0.5v at idle. If it doesn't, what does it read? Also, check your idle LTFT value and see if it's way above or below 100%.

What do the plug tips look like?

I just logged my Front o2 volt today and it sat at a steady 0.00v, does this mean my front o2 sensor is bad? Looks like this is my problem instead of my ISC like I initially thought.

 

[BOC Jason]

The o2 should cycle at idle, from lean to rich constantly. My o2 was bad but my car didnt have any of the symptoms that your describing. Have you looked under the hood for an overview. One time my stock intake pipe had a big gash in it causing me to run rich all the time and run like crap.

What are common things that could cause to to run rich?