Check engine light came on on Monday.

When accelerating, there was a lot of hesitation in the throttle, particularly in the low rpms. Turns out the o2/laf sensor went bad.

Got the car back last night. I swear it's a whole different animal. Acceleration is very responsive, and smooth.

Thinking back, I don't think it ever drove this good. There was always a slight hesitation. Wonder if there's always been a problem with it, but not enough to throw a code.

And this may sound odd, but even my shifts are better. I can match the revs really well and much smoother. Before, seemed like no matter what I did, the shifts were always a little rougher than they should be. Was actually a pet peeve of mine, but no more.

Only question, seems odd that the o2 sensor went. Car is 18 months old, with 25000 miles on it.

 

Hmmm that does seem odd. But glad it got fixed for you.

What type of fuel are you using btw? Sometimes unburnt or "dirty" fuel can ruin a good 02 sensor. Just wondering

 

I replaced my air fuel sensor as well they screwed it up when they installed my headers...

The car was running like crap on the dyno during all 3 pulls it had trouble with each climb.

 

Happens. I replaced both of them on mine. And yes, driving is dramatically improved. It gets even worst than driving around with 87 octane IMO.

 

Aren't there two O2 sensors or am I mistaken? Which one went out on your car? I have a 6MT and have felt lack of power and hesitation off and on at lower rpms. I changed the air cleaner element which seemed to help (it was very dirty even though I have only about 16K miles on the car) but I still feel it at times. I tried different gas, gas stations and am sticking to Chevron premium for now. But that hasn't made a difference. I am wondering now if the O2 sensor(s) are in need of replacement. No check engine light yet.

sauceman: did your check engine light come on before you replaced them?

Thanks!

 

Honestly, have no idea which sensor it was. Actually, they confused me initially as they called it an auto laf or something, and I didn't realize it was just the o2 sensor.

Always used premium gas.

I wonder if it's been a little flaky from the beginning. Definitely haven't been pleased with the car's performance the past few months. But I think it got worse so gradually I didn't really notice. Much better now though.

 

a broken o2 sensor means your ECU can no longer properly check its air/fuel ratio..thus it throws the car into what they usually call "limp" mode... the ecu will then think safe and throw in more fuel to run rich to be safe... this is so the engine does not detonate... therefore you get a loss of power.

this is for the o2 sensor in the header..if its the aftercat o2 sensor... that o2 sensor does not usually affect anything except it serves to see if the catalytic converter is working correctly.

 

I replaced them after having CELs come up. The second CEL appeared only after I was experiencing severe misfire in one or more cylinders. The car could absolutely not accelerate, even in 1st gear. It felt a little like when a fuel filter clogs up.

I shut the engine down for 5 minutes, restarted, everything was going fine, then 50km later the CEL came on.