P0131 - Car Surging?

OK - So I know P0131 = Front O2 Sensor reads low....

 

Will be making an appointment with local shop to change the sensor - but here's the odd question on symptoms:

 

The car actually surges while driving down the road -as if stabbing the gas and letting off - and it seems to take a second for boost to build but once it spools - it's normal and hit full boost like nothings wrong.

 

But off boost and light throttle car surges - steady light throttle you can actually feel it pulsing...

 

I assume by the code the O2 sensor is the culprit - but just wondering if that would actually cause these symptoms - and O2 Sensor was replaced 20K ago with Bosch sensor been running fine since new engine/build? So could it be vacuum leak? Bad EBC?

 

The last time the O2 went - car ran fine with the check engine light on but clearly this time it's different:confused:

 

I ask as the local shop is great at general work - but not Subaru experts - and the car will not see a dealer and I would only trust ESP if it had to go to a full on expert - but I hate towing the car there as it's a ways and a pain (but certainly an option if needed) - So is it worth trying to swap the O2 sensor locally?

Yes, a bad O2 sensor, or in this case the WRONG O2 sensor, will cause these symptoms. Your car needs a Denso sensor ONLY. See the sticky for the part number.

You can totally replace it yourself, very easy job. You just need a breaker bar and an O2 sensor socket, both available cheaply (or probably even as loaners) from your local auto parts store.

 

If you're wondering why it drives fine under boost at WOT, that's because under those conditions it's in open loop mode, no longer using the O2 sensor's input to calculate fueling.

Would it have to be towed to somewhere like ECS in Windsor Locks? Not sure how far from them you are. ecs-performance.com

E. Granby CT is just a few miles from ECS, it's the next town over.

 

But yes the Front sensor is easy to replace.Pull the right front wheel, pull the plastic panel. its right there.

Thanks Guys - as I looked further online it does seem like surging while driving is a classic bad O2 symptom - so I'll have the local shop swap it out.

 

As to ECS - well the car has seen their shop multiple times - but I was never fully happy there - and the experience at ESP was so much better - that they've won my business...

 

But with the latest complete engine rebuild from ECS the car has been solid - hence the extra concern over what seemed like an odd issue - but seems pretty simple and easy.

Just got the car back - Turned out to need an 02 Sensor & MAF Sensor.

 

 

All back in order!

Yes, a bad O2 sensor, or in this case the WRONG O2 sensor, will cause these symptoms. Your car needs a Denso sensor ONLY. See the sticky for the part number.

You can totally replace it yourself, very easy job. You just need a breaker bar and an O2 sensor socket, both available cheaply (or probably even as loaners) from your local auto parts store.

 

If you're wondering why it drives fine under boost at WOT, that's because under those conditions it's in open loop mode, no longer using the O2 sensor's input to calculate fueling.

 

FYI the Bosch are Denso O2 sensors. I'm running a Bosch on my STG2, zero issues.

Bad front O2 definitely causes surging, and many times without setting a code. Find a known good one to try before purchasing a new one, but about 99 times out of 100, that will be the surging. Look at your STFT and it will be bouncing all over the place.