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Discussion Starter #1
Alright, I'll explain how I got here in a minute, but BLUF: Does anyone know if the 2012 EGR reported error on the OBD is actually an EGR position sensor? OR is this somehow a calculated EGR error taken from O2 readings and what not?

TLDR Version...

  • A while ago started having sporadic "slow starting" problems...
  • Mechanic changed plugs (waste of money, they are iridium I think and I was around 60k at the time) - did nothing..
  • Recently, that escalated to occasional cold stalls. In the first 5 minutes (or less) of driving, coolant temp below 160 or so (seems to be the worst, per the OBD), if accelerate a bit and stop (i.e. pulling up to the first stop sign on a drive) it seems to stall somewhat reliably.
  • Changes the air filter and cleaned the throttle body - no change in behavior
  • Other evidence - Occasional lack of acceleration followed by a sudden jolt. Gas mileage is definitely down a few MPG from where it should be (getting ~18-19 average on a 80% highway but frequent traffic commute... would expect at least the city 21 or a little better for my driving) hard to say how long these ones have been around... possibly I've been ignoring it for a while and am just noticing how that I'm looking for stuff
  • Finally got a bluetooth OBD reader instead of the USB one so I can lot some stuff on my phone...
  • Getting values all over the place for the reported EGR error (using Torque Pro to monitor and log). Also, the air/fuel ratio seems to be peaking somewhat abnormally (sometimes up to 18 or so, then settling back down to 14). Trying to figure out if I definitively know cause and effect yet before I started a) cleaning my EGT valve or b) otherwise hunting down a vacuum leak somewhere
Anyone know... is that error a 100% problem with the EGR valve or sensor? Or is it possibly a secondary indication of something else? (i.e. is it a calculated value as opposed to a direct measurement) I have charts and logs galore if data would help... I make sure this morning to jot down a few time stamps, so I've got a cold idle both in Park and Drive, a Warm idle in both as well as a cold stall..... Just let me know what would be helpful to see! And Thank you!
 

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I would use your OBD2 scanner and log Long Term Fuel Trim and see where it's at. It's easier to see how lean/rich you are running with LTFT.

Check 02 sensor voltage in Torque Pro
Check Vehicle Voltage with Torque Pro.
Check Fuel pressure if possible
 

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Discussion Starter #3
I didn't think LTFT looked out of wack (based on my uneducated googling of what it should swing around)... What do you think? this is this morning's commute (First half was more stop and go, second half was steadier highway.. not interstate, but steadier than the first half):
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Here's the O2 sensor voltage (or at least the filed I had set to log this morning).... Let me know if those spikes are abnormal if you could... or if there's a different field I should grab from Torque for next time:
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I've also got the data timestamped right when I stalled this morning... So far, everything seems to change after the stall, not leading up to it. Possible exception being the vacuum pressure - that isn't sampled quite fast enough to tell even at ~3Hz it seems I was getting this morning (selected the faster update option in torque and limited what I was logging):
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I didn't log vehicle voltage, but can add for the way home. Fuel pressure didn't seem to be available in the standard OBD PIDs... Torque doesn't have custom Subaru ones... couldn't find that info online anywhere for those PID definitions, seems Subaru does a better job keeping that secret than other manufacturers?

Thanks!
 

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@pbennett453 I take it this is the AF sensor, the heated O2 sensor before the cat? So Bank1, Sensor1 - the upstream sensor?
It looks saturated when it slams to 5V and ground. I take it the car has warmed up so in closed loop? Even in open loop, it shouldn't slam to those voltages. The average voltage also doesn't look right to me. It is hard to say what the time base means - seconds, I take it?

Looks like a bad upstream sensor to me. I noticed you suspect a bad EGR but I'm not sure whether that will have that kind of effect on the O2 readings.
I could be wrong, tho..
 

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Discussion Starter #5
I take it this is the AF sensor, the heated O2 sensor before the cat? So Bank1, Sensor1 - the upstream sensor?
It looks saturated when it slams to 5V and ground. I take it the car has warmed up so in closed loop? Even in open loop, it shouldn't slam to those voltages. The average voltage also doesn't look right to me. It is hard to say what the time base means - seconds, I take it?

Looks like a bad upstream sensor to me. I noticed you suspect a bad EGR but I'm not sure whether that will have that kind of effect on the O2 readings.
I could be wrong, tho..
Thanks for the input. Not entirely sure.. that's the PID name that Torque calls it.
As for the time base - that was prior to figuring out how to convert the time to seconds. But that is about a half hour drive across the full span of that O2 plot. Note... 2012 is a wideband sensor, not a narrowband.... although the spikes do seem wrong and loosely correspond to spires in the A/F Ratio reading, not sure if those are both read off ODB or if Torque is calculating one of those. Another view below...

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Of course... none of that O2 / AF spiking at started yet when the car stalled at 250 seconds.... which is why I'm concerned I haven't actually unraveled cause and effect yet....
 

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I thought if you are seeing 5 volts on the 02 sensor that means there is a short in that system. But maybe Subarus are different.

and the AF spikes match the 02 Voltage spikes.

As said above, I'd replace the upstream 02 sensor.
 

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Discussion Starter #7
For anyone following this.... I took it in for a couple old recalls I had been ignoring and had them look at it.. just ran out of time to keep troubleshooting myself unfortunately. They are saying A/F sensor (upstream O2) but unfortunately it's because the cam carrier seal is leaking on it.... which is an over $3k job at the dealer. It's out of warranty, so I'll shop around a couple of local mechanics... but still... yikes. I'll post another threat to get advice on that job instead of tagging onto this less related one. Just figured I would put the info down for anyone browsing it.
 
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