symptoms of a bad o2 sensor.......

[Vegas Smith]

symptoms of a bad 02 sensor.....my car has severe hesitation....gets sub-par gas mileage and smells rich.......but here is the tricky one. i have an a/f gauge.....it used to work but a few months ago it just stopped working, tried diferent fuses ect....just doesnt work anymore, but still lights up so i know its not the gauge. ironically this was about the same time my car started going downhill, could it be that the o2 sensor just plain blew out, and when i hit boost the car becomes too lean or too rich, causing hesitation?

 

[Eclipsor16G]

Hesitation should not be caused by a faulty O2 sensor. The only time the O2 sensor is actually in use is at idle and cruise (not WOT), and only under 4500 RPMs (I think). This is when the car is in "closed-loop" mode. The O2 sensor monitors how much oxygen is in the exhaust and finely adjusts the amount of fuel being injected into the cylinders to achieve a stoich mixture. At full throttle the O2 sensor is not used at all. Instead, fuel calculations are made (for the most part) based on the airflow reading from the MAS. This is called "open-loop" mode. Bad gas mileage is a tell-tale sign of a faulty O2 sensor, but I'd say you have other problems.

Chris

 

[Vegas Smith]

well that settles that, but what about the a/f gauge, do you think that is because the o2 went out? thanks

 

[Eclipsor16G]

Could be... but you'd be getting a check engine light that indicated a faulty O2 sensor. How many miles has the sensor been on your car? Do you ever use leaded gasoline?

Chris

 

[Vegas Smith]

i talked to my bro and he said he put a new one on about a year and a half ago. i only use 93 octane.

 

[jb95gst]

Hey I am also experiencing a problem with my mpg. Is there any way to test the o2 sensor to see if it is bad. I do not have a CEL, but my mpg sux and I have noticed on my a/f guage when I let off the gas it goes to rich and stays over there for a few seconds before going to lean. It never used to do that. I noticed it after I gutted the cat and put a straight pipe through it. I still have stock exhaust, and I don't vent to the atmosphere. This happened before and I replaced the spark plugs and it went back up some, but now it's heading down, that was like a month ago. Thanks, JB

 

[90turboedcelica]

What ended up being wrong with you car that was causing it to hesitate when you hit boost because I am experiencing the same problems.

 

[my dreamt dsm]

This is an old thread back in 03.
Check your fuel pump. I am also having the same issue plus a lot of knock.

 

[90turboedcelica]

If your having a lot of knock check you knock sensor and see if its bad.

 

[Tony818]

What ended up being wrong with you car that was causing it to hesitate when you hit boost because I am experiencing the same problems.

Did you ever figure this out? I been reading nonstop, and tries so many things with no results

 

[brian9397gsx]

Did you ever figure this out? I been reading nonstop, and tries so many things with no results

Old thread I'll go out on a limb and say that he wont respond.
For your issue you need to start with the basics. Boost leak test and a proper go over of your ignition system. I was fighting a lean breaking up issue with mine that turned out to be 2 of my brand new plugs had hairline cracks in the porcelain.

 

[Gwaihir]

Boost leak test, plugs, fuel filter are good places to start. I had hesitation when I first bought my car when applying throttle. Major boost leak at the BOV and then another where a T was installed for the boost gauge. Fixed those and hesitation went away.

 

[Tony818]

Boost leak test, plugs, fuel filter are good places to start. I had hesitation when I first bought my car when applying throttle. Major boost leak at the BOV and then another where a T was installed for the boost gauge. Fixed those and hesitation went away.

Thanks for the reply. My problem is that my car goes to 7 AFR when I go into boost. I have no boost leaks, I changed 2 different maf, I checked injector voltage, and had them flow tested and cleaned, I'm running out of ideas. I wonder if a bad o2 sensor would cause this. But wouldnt it throw a code?

 

[Vegas Smith]

Thanks for the reply. My problem is that my car goes to 7 AFR when I go into boost. I have no boost leaks, I changed 2 different maf, I checked injector voltage, and had them flow tested and cleaned, I'm running out of ideas. I wonder if a bad o2 sensor would cause this. But wouldnt it throw a code?

What mods does the car have? How are you tuning? What fuel pump/injectors/fuel pressure regulator do you have?

 

[Tony818]

What mods does the car have? How are you tuning? What fuel pump/injectors/fuel pressure regulator do you have?

No mods. Car is basically stock. I stroked it to 2.3, i have a 3 inch exhaust 3 in cat and a 2.5 o2 housing. Fuel pressure regulator is oem and seems to be working fine. Tunning wise I have ecuflash but I have not messed with tunning yet.

 

[Vegas Smith]

And you have a wideband installed?

 

[Tony818]

And you have a wideband installed?

Yea innovative lc1

 

[Vegas Smith]

That's funny....I just realized that I started this thread 16 years ago.....

 

[Tony818]

That's funny....I just realized that I started this thread 16 years ago.....

Lol good to see your still in the community tho hahah normally ppl will just quit. Blame crankwalk and move on

 

[Tony818]

I'm really trying to get my car running right. But I'm at the point of giving up on it. I cant find nowhere online that can answer why my car is running rich ONLY in BOOST. Normal driving is good but once I step on it my Wideband says I'm running RICH and maxed out at 7:1 AFR. And the car has no pwer

 

[Vegas Smith]

I'm guessing you have a big boost leak as air will leave the engine but you still have all the fuel being dumped in. Do a boost leak test and see what you find.

 

[Tony818]

I'm guessing you have a big boost leak as air will leave the engine but you still have all the fuel being dumped in. Do a boost leak test and see what you find.

I did. I did a boost leak test at the throttle body, and at the turbo inlet with no leaks.

 

[Tony818]

Regulator seems to be working fine, fuel injectors are clean and voltage is right, do you think the injector resistor might have something to do with the car running rich? I kinda doubt it

 

[Vegas Smith]

Hmm, I'd be surprised. You may have a big exhaust leak causing the car to run rich. Some of your turbo/manifold/o2 housing gaskets are leaking and that's tricking your o2 sensors.

 

[Tony818]

Hmm, I'd be surprised. You may have a big exhaust leak causing the car to run rich. Some of your turbo/manifold/o2 housing gaskets are leaking and that's tricking your o2 sensors.

You sir . . . May be right. I'm sure no leak there. But I'm definately gonna check. . . But how do you check exhaust leaks?