I'm fighting an '11 Forester normally aspirated that had a no-start/very hard start. Now it's starting relatively easily but idle sucks sometimes and it's recording misfires in 1 and 3. Common problem on all the Subaru engines from what I've seen.
There's often talk of the O2 sensor causing misfires but how would this affect cold start? As I understand it the ECM isn't looking at HEGO for starting purposes, at least cold?
I'm only curious about O2 because if I unplug the upstream no more misfires are recorded, but I'm not sure it actually runs or idles much better. Will the ECM even try to record misfire counts if the O2 is disconn'ed?
Basically I'm wondering if I'm creating a red herring by looking at misfire counts with and without O2 sensor?
I've gone through a lot of other troubleshooting but in the interest of brevity (too late!) I'd rather not get into that here. Just wondering if it's significant that misfire counts stop with O2 unplugged?
There's often talk of the O2 sensor causing misfires but how would this affect cold start? As I understand it the ECM isn't looking at HEGO for starting purposes, at least cold?
I'm only curious about O2 because if I unplug the upstream no more misfires are recorded, but I'm not sure it actually runs or idles much better. Will the ECM even try to record misfire counts if the O2 is disconn'ed?
Basically I'm wondering if I'm creating a red herring by looking at misfire counts with and without O2 sensor?
I've gone through a lot of other troubleshooting but in the interest of brevity (too late!) I'd rather not get into that here. Just wondering if it's significant that misfire counts stop with O2 unplugged?