I've had some strange things going on with my R53 the last few months. I'll be driving down the highway with the cruise control on at a constant speed......then all of a sudden I can feel the engine surging a little bit, and the ARF (on my wide band 02 gauge) starts jumping up and down from around 12 to 16....and then after a few seconds of that, it settles back down to around 14.7-15.0...where it's supposed to be at cruise.



There are no codes, no CEL's, nothing that would indicate a problem.



Is this the indication of a bad 02 sensor, or one starting to go bad? Not sure why the air fuel ratio would start jumping around like that. I know that the R53's are in closed loop when cruising, and open loop at idle and WOT.....so it's really only using the factory narrow band O2 for fuel mixtures at cruising speeds/loads. Can I have an 02 that is failing, and NOT setting off a check engine light?



Thoughts?

 

Does sound very similar to when my pre-cat o2 sensor went. However, I was also throwing codes and had instances withing a couple minutes after starting the car, it would almost stall out on me while driving. Start it back up again and it would drive fine other than the surging and lack of power. I found one of these as a replacement.

 

Do these R53's have just one 02 sensor before the cat...or one before, and one after? If one of the O2 sensors was acting up.....would it throw a code, or is there a chance that it wouldn't?

 

Before and after, the gas mileage starts to dip then you will get a cel. Thats what mine did.

It does not throw a code at first. I would do both as it saves time.

https://www.northamericanmotoring.co...placement.html

 

Who’s / what wide band do you have? The innovative ones which are are Bosch O2’s need to be reset every one in a while.

My car runs off my wide-band wired directly to my ViPEC along with my Aquamist Meth kit.

When my wide band reads goes that low I reset the wide band. Some times the Bosch wideband fails and they only cost $93 versus the cost of a OEM narrow band O2.

https://www.innovatemotorsports.com/...cat=250&page=1

I do this by removing it from my header, still plugged in to its connection. Then power it on via the key and let it take an open air sample so it can recalibrate and get it’s settings. Then you reinstall it and do the same thing and let it take its exhaust sample and it resets itself.

You should also scan your car and see if either OEM O2 (pre and post Cat) are throwing codes. If they are replace with OEM O2’s. The OEM ECU can be very picky about the cheaper ones people sell. NGK / NTK O2 are recommended. NO BOSCH O2’s.