2011 Subaru Forester shaking when at stoplights

[beckym]

I have a 2011 Subaru Forester, about 156,000 miles. 

Last year my CEL came on and the Subaru dealership found that the catalytic converter need to be replaced. Luckily my vehicle was a PZE model, so this was under warranty. That work has been done, but for the last 6 months or so my car will shake heavily while at stoplights or slowing down and the CEL will come on - solid light. The code it's throwing is almost always about misfire of spark plugs. Sometimes the light goes off before I can get to Subaru so they can't always read the code. I've had new spark plugs since June but today the shaking started back up again, and the solid CEL is on with a solid traction control light and flashing cruise control light. Any thoughts?? 

[beckym]

I would greatly appreciate any thoughts or suggestions anyone might have. 

[idosubaru]

1 hour ago, beckym said:

I have a 2011 Subaru Forester, about 156,000 miles. 

Last year my CEL came on and the Subaru dealership found that the catalytic converter need to be replaced. Luckily my vehicle was a PZE model, so this was under warranty. That work has been done, but for the last 6 months or so my car will shake heavily while at stoplights or slowing down and the CEL will come on - solid light. The code it's throwing is almost always about misfire of spark plugs. Sometimes the light goes off before I can get to Subaru so they can't always read the code. I've had new spark plugs since June but today the shaking started back up again, and the solid CEL is on with a solid traction control light and flashing cruise control light. Any thoughts?? 

We need the codes - the exact number.  Any national chain like NAPA, Advance Auto Parts, Autozone, OReillys will read the codes for free. 

Have them read there and then post the 4 digit numbers here like P0303, P0302....don't post what the shop says could be causing it or their brief description - give us the actual numbers like I just posted.

You can even buy a cheap code reader for like $30 or less on ebay.  Fits in the glove box or spare tire area, very easy to use, and saves time/trips/quicker info/diagnosis.  You can even get a phone adapter for cheaper if you want to play with getting one of those and downloading and app for it on your phone. 

 

 

Edited September 11, 2019 by idosubaru

[GeneralDisorder]

Check that the front AFR sensor harness isn't soaked with oil from a chain cover leak and caused the sensor to fail. This can result is heavily positive or negative fuel trims and can contribute to catalyst failure. There's a TSB about this from Subaru. A misfire condition WILL damage that new catalytic converter so you need to get it into a (preferably independent Subaru specialist) quickly to get it diagnosed. It's most likely a fuel trim problem like an intake air leak, bad PCV valve, dirty MAF, or failed front AFR sensor. You cannot diagnose this without special equipment and we can't do it through the internet either. The misfire and the converter failure are probably related and the dealer didn't address the underlying cause. 

GD

Edited September 11, 2019 by GeneralDisorder