O2 sensor question

[Chriskaw440]

I'm thinking that my O2 sensor may be fouled (from engine running a bit rich for a long time thanks to a bad temp sensor that has since been replaced) and causing my crappy idle while warming up

in the mornings and maybe my often at times erratic idle jumping to almost 2,000 rpm and then settling back down to normal.

 

O2 sensor is only about 3 years old.....and my ECU flashes "55" (normal) Does seem plausible for those symptoms...when most everything else is new or cleaned?

 

thanks...just still trying to solve these issues.

[MY1PATH]

un-plug it, if things get better that is a sign it needs replaced.

They usually don't throw a code when they fail.

[Precise1]

^ Exactly.

 

Also, check for EGR valve function, vacuum leaks, clean the MAF, etc. All free and easy, eliminating possible problems.

 

B

[sewebster]

The ECU has a O2 sensor test mode right? You should be able to use that to see how messed up it is? Or if it just isn't working at all?

 

My understanding of the sensors is that they do a little "oscillation" when working properly. The test mode blinks the light when it oscillates and you count the number in 10 seconds. The manual tells you how many is acceptable. If you get none then that's bad for instance. Kinda going off memory here.

[nige]

the FSM outlines how to test the functionality of the O2 sensor. I think you need a multimeter and a paperclip to jump the terminals.

 

FYI i'm on my 3rd o2 sensor. the first one threw a code, the second one didn't I unplugged the second one and the truck ran better, so i replaced it. I need to test the one i currently have because my engine is running rich.

[adamzan]

The Bosch ones suck. I would get a Nissan one if possible. I'm on my 2nd Bosch one after the first one failed while I was far from home and running rich all the way home killed my cat as well.

[Chriskaw440]

The Bosch ones suck. I would get a Nissan one if possible. I'm on my 2nd Bosch one after the first one failed while I was far from home and running rich all the way home killed my cat as well.

 

if I remember right....I got a Bosch one.

 

thanks for the tips. I cleaned the MAF sensor already but I am still suspicious of how 'well' its actually performing since its the original, 20 years old now...

 

Im thinking this could be why, for the first 30 seconds to a minute, the truck idles great when cold, then it turns to sh*tty sputtering idle, until its fully warmed up for the most part....

 

takes a few moments for the ECU to get a signal from the sensor??

[Chriskaw440]

Rock Auto Parts has quite a few brands on closeout..... NTK, Beck Arnley, and Standard Motor Products...... ranging from $49.99 to about $60.00..... and $99.00 to $107 (bosch most expensive...) for regular stock.

 

If mine is shot I'll probably go with one of the first three. I know getting one from my Nissan dealership around here will be $$$$

[adamzan]

Beck/Arnley usually makes pretty good stuff.

[Kingman]

if I remember right....I got a Bosch one.

 

thanks for the tips. I cleaned the MAF sensor already but I am still suspicious of how 'well' its actually performing since its the original, 20 years old now...

 

Im thinking this could be why, for the first 30 seconds to a minute, the truck idles great when cold, then it turns to sh*tty sputtering idle, until its fully warmed up for the most part....

 

takes a few moments for the ECU to get a signal from the sensor??

 

Up until 150F, the computer runs the engine in open-loop mode with no inputs from any sensor, just a pre-set mapped ratio. After that is when closed-loop is activated and the computer takes constant readings from the various sensors, O2 sensor being one of them.

[Chriskaw440]

Up until 150F, the computer runs the engine in open-loop mode with no inputs from any sensor, just a pre-set mapped ratio. After that is when closed-loop is activated and the computer takes constant readings from the various sensors, O2 sensor being one of them.

 

any ideas why then the idle would be so crappy after about a minute of starting (cold) until its warmer? practically everything has been replaced with new parts.

 

also....the longer I drive it around town (5 speed tranny by the way) the more the idle wants to jump up to almost 2,000 rpm when taken out of gear. Sometimes I can even feel it do this

when I am driving at a slower speed while in gear...its like feeling the engine start to 'pull more' when I am not giving it any more gas, or even starting to slow down....then I take it of gear

and it races up to almost 2,000....then eases back down to where its normal and purrs like a kitten.

[Kingman]

Shouldn't be O2 sensor related, it only sends the computer a 0-1V signal depending on how rich the exhaust is. MAF, TPS, and a sticky throttle cable/linkage at the throttle body can do that.

[Chriskaw440]

Shouldn't be O2 sensor related, it only sends the computer a 0-1V signal depending on how rich the exhaust is. MAF, TPS, and a sticky throttle cable/linkage at the throttle body can do that.

 

It looks like its my TPS may be a bit squirrily, as it was idling today and I was checking things out....working the throttle body open and shut, it was running beautifully, so I started tapping on things with the handle of my screwdriver and if I tapped on the TPS much it would throw the idle up higher and get stuck there. Sometimes it would...sometimes it wouldn't

 

It is a new one, so I loosened the two screws that hold it in place and did a slight rotation until it idled better and test drove it a couple miles stop and go driving and it seemed fine. So we'll see how it goes after a few days.

 

When I unplugged the MAF sensor the engine died immediately. Is that a normal thing to happen if you unplug the MAF?

[Precise1]

any ideas why then the idle would be so crappy after about a minute of starting (cold) until its warmer? practically everything has been replaced with new parts.

 

also....the longer I drive it around town (5 speed tranny by the way) the more the idle wants to jump up to almost 2,000 rpm when taken out of gear. Sometimes I can even feel it do this

when I am driving at a slower speed while in gear...its like feeling the engine start to 'pull more' when I am not giving it any more gas, or even starting to slow down....then I take it of gear

and it races up to almost 2,000....then eases back down to where its normal and purrs like a kitten.

I was going to mention that I am guessing TPS. Mine (auto tranny) would sometimes run 1000-1100rpm in park. I wiggled the connector for the TPS and instant response; idle drop to 750...

 

I don't know about dying when the MAF is unplugged, I thought it generally stumbles but have never needed to do it myself.

 

B

[Kingman]

It should have gone into a fail-safe mode if the MAF was unplugged, and not rev above 2,000 RPM. Not just die...

 

I would take it dying with a large grain of salt though.