07 Legacy, delayed O2 AFM Startup.

[nickmcgill]

Hi Team,

 

I've been troubleshooting an issue for awhile with my O2 AFM.

Symptoms is delayed reading of the O2 sensor after startup.

Brand new 4 wire O2 sensor has been installed after the last one appeared intermittent. 

After starting the car it will read at 14.7 for between 8-10mins on average then seems to work as expected. 

 

First we thought that it might be an issue with the heater. 

Jason (gotasuby) and I did some tests and found the ECU wasn't providing an earth for the heater.

After shorting the heater circuit to ground to force it to heat we found the ECU still didn't take a reading from the sensor. 

We were alternating the heater circuit on and off but didn't want to do it for a long period of time to avoid any damage. 

 

Can any other 07~ owners let me know if they have noticed similar behaviour on theirs ? 
Mine will do this regardless if its a cold start or a hot start.

[Kiwi_Fozze]

Yep, my 3.0r did. Took about 10 mins after startup (hot or cold) to read actual afr's, until then it pegged 14.7

 

I assume it to be part of the warmup processs

[Andy_Mac]

Yep. Measured the time taken a while back, can't remember exactly, somewhere north of 5mins usually.

Been looking at some logs of another member on here recently regarding unrelated missfires and they had it taking 9+mins. 

Seems extremely weird, had thought a new one might fix it but you've nicely spent the money and saved the rest of us from trying that option

The ECU must have a hard time determining fuel trims without it running. Especially when the engine is up to temp well before it starts reading. Doesn't make sense to me..

[nickmcgill]

I also assumed it might be part of the warm up process and run off the other sensors available plus learnt values in the mean time. 

Some said they should be reading in less than a minute, might depend on the make/model. 

 

 

3 minutes ago, Andy_Mac said:

Yep. Measured the time taken a while back, can't remember exactly, somewhere north of 5mins usually.

Been looking at some logs of another member on here recently regarding unrelated missfires and they had it taking 9+mins. 

Seems extremely weird, had thought a new one might fix it but you've nicely spent the money and saved the rest of us from trying that option

The ECU must have a hard time determining fuel trims without it running. Especially when the engine is up to temp well before it starts reading. Doesn't make sense to me..

My tuner mentioned to me that he thought the fuel trims were a bit weird after doing the tuning, I suspect this is why. 

I was hoping a new sensor would fix it too, hopefully its not needing a new ECU too 

[sobanoodle]

37 minutes ago, nickmcgill said:

I also assumed it might be part of the warm up process and run off the other sensors available plus learnt values in the mean time. 

Some said they should be reading in less than a minute, might depend on the make/model. 

 

 

My tuner mentioned to me that he thought the fuel trims were a bit weird after doing the tuning, I suspect this is why. 

I was hoping a new sensor would fix it too, hopefully its not needing a new ECU too 

On a side note - did you get your gearbox issues sorted? 

[nickmcgill]

8 hours ago, sobanoodle said:

On a side note - did you get your gearbox issues sorted? 

 

Its a work in progress
I've learnt a lot about them over the past couple of months about what they do and don't like. 

It looks like the fluid that was put in might be the problem, but can't confirm this until we swap it out. 

Will be getting a flush done in the next month or so with the OEM ATF or the NZ available equivalent. 

 

I'm hoping its not a valve body problem, although seems very coincidental to have the issues as soon as the fluid is changed. Watch this space.