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Bad front 02 sensor?

4.2K views 6 replies 3 participants last post by  staticx313  
#1 ·
I remember a WHILE back, when I first got my car, that some people had 02 sensor problems, said that the ride was really bad and what not. No CEL. They took it in and to their surprise it was a bad 02 sensor (front 02). I was wondering... whenever i let off the gas it seems to lunge forward really hard... like massive recoil. Stock bov, new turbo, etc.. putting redline in the rear diff smoothed it out (thank goodness), but its still there.. anyone have nay ideas? This may also explain why the turbo kinda "unspools" still in first gear when shifting at low rpms... Its obviously not the turbo (as its brand new vf34), i've replaced the IC gaskets, so now im wondering if this is it. Anyone think Im on the right track? Also how much is an 02 sensor? I may just replace it just in case. Thanks... btw is there a way to check it?

Robert~
 
#2 ·
anyone?

Also if you may know that the recoil is normal or if it may just be because of my mods, lmk... otherwise, any help would be GREAT!

Robert~
 
#3 ·
i heard a few people that ended up replacing the o2 sensor but i think that was the rear bank...which make's me believe becasue of the cat issue...but as far as the front im not sure of the story...could of just went bad...
 
#4 ·
hmmm so can ayone help me narrow this down? what would be causing a recoil on letting off the gas? Pitch mount? Engine mount? Tranny mount? Tranny fluid low? Clutch? Whiteline rear diff bushings?

Robert~
 
#5 ·
guess i'll be figuring this one out on my own... is there a way to test the 02 sensor to see if it works correctly? Also, where do you guys think i should start. Does anyone else have recoil when letting off the gas?

Robert~
 
#6 ·
Hello Robert,

Your description is rather vague but here's what I am guessing it might be. Lower gears have a high numerical ratio which means that they create more engine braking when the throttle is released.

If you push the gas hard and release abruptly there will be a corresponding change of direction which can be quite violent due to the engine braking effect.

Compounding this effect are these factors;

1. If you are used to six or eight cylinder cars, the engine mounting systems of four cylinders typically have a lot more driveline lash because of the requirement to dampen more noise, vibration and harshness (NVH). AWD further complicates things because you have differentials, driveshafts etc.. at both ends of the car. This means that the drivetrain moves around a lot with abrupt throttle transitions. This can be felt in the car because you are talking about 300-400lbs (albeit rubber mounted) banging around under the hood.

2. High numerical gear ratios are more common in four cylinder turbo cars than other cars.

3. A BOV vented to atmosphere will create difficulties for the ECU because it creates an "accounting" error for airflow. This could manifest itself in an engine bucking or stalling condition.

4. As part of an emmissions reduction strategy, the throttle on the STi will not close immediately (even if you let off completely) under some conditions. You may be experiencing sensations related to this anomaly.


You might find that replacing the engine and trans mounts with the STi products will alleviate this sensation in exchange though for increased NVH.

Regarding your original O2 sensor question - O2 sensors are quite durable, unless your car has 60K+ miles on it or you have been running leaded gas or a ton of octane booster, it is unlikely to have failed.

You can check for yourself by warming the car up and checking the 02 sensor voltage at the ECU connector. ( you would need a pinout diagram) or get a friend with an OBD2 logger to check its operation.

Hope this helps.
 
#7 ·
hmmm the thing is , was that when i first got the car, someone on NASIOC was complaining about a jerky ride or something and they sadi that the 02 sensor was bad from the factory (front one)and it was somehow reading the a/f wrong and would cause the jerkiness. Im not sure. I will just keep upgrading bushings and what not and see what happens. Thank you for your help! (I understood this happening with the bov in, but not with the stock bov).

Robert~