2001 Forester - Misfire Codes - Major Bucking

[Tony Cortado]

Hi all! I am wondering if someone can help me diagnose my car issue! I have a manual 2001 foz. It's throwing misfire and sensor codes. From acceleration or driving at slow speeds, there is major bucking, so much that I need to rev it up to get going - which occasionally includes a backfire or two.  I got the codes checked out and replaced the Ignition coil as suggested, but that didn't change much. The spark plugs and wires are about 3 years old. No idea on the age of any sensors (bought it used 3 years ago!). Below you can see all the codes that were presented. Anyone know how I can diagnose this?

Thank you!

Edited July 9, 2021 by Tony Cortado

[GeneralDisorder]

Replace the coil, plugs, and wires with OEM parts from Subaru. 

Also need fuel trim data. Probably running lean. Knock sensor may be boned. Hard to say without real time data. 

GD

Edited July 10, 2021 by GeneralDisorder

[nipper]

I was going to say look for a common denominator, the knock sensor

[Ferret54]

Here’s a link to my EGR write up on the Forester board years ago....

http://www.subaruforester.org/vbulletin/f88/low-idle-stuttering-erratic-jerking-various-rpms-76450/index3.html#post887065

 

[1 Lucky Texan]

knock sensor needs attention.

 

I wouldn't rule out partially clogged exhaust. Vacuum gauge might show that.

[nipper]

1 hour ago, 1 Lucky Texan said:

knock sensor needs attention.

 

I wouldn't rule out partially clogged exhaust. Vacuum gauge might show that.

Everyone should own a vacume gauge, cheap easy to use and often overlooked.

[GeneralDisorder]

1 hour ago, nipper said:

Everyone should own a vacume gauge, cheap easy to use and often overlooked.

And with a SIMPLE adapter, most vacuum gauges can also read low pressure and can test for exhaust back-pressure when adapted to the bung of the front O2. Which will immediately show a plugged exhaust condition. 

GD

[nipper]

11 hours ago, GeneralDisorder said:

And with a SIMPLE adapter, most vacuum gauges can also read low pressure and can test for exhaust back-pressure when adapted to the bung of the front O2. Which will immediately show a plugged exhaust condition. 

GD

You dont really need the bung adapter for that, but true.

[Tony Cortado]

Those of you that said knock sensor were spot on!  After reading your suggestions and noticing that the knock sensor is one of the first codes to show up, it makes total sense in hindsight that the knock sensor would send adjustment info to the computer, thereby messing everything up. I took it out and laughed pretty hard, because the plastic casing around it was almost totally demolished, and the sensor itself had some rust around it. Needless to say, after $30 and ..... 6 minutes of replacing the part, I'm back in business!  Check engine light has been off for 5 days! Thanks everyone!

Edited July 23, 2021 by Tony Cortado

[1 Lucky Texan]

5 days,,,,, that should be past the monitors completing . Still, you could have other maintenance to 'catch-up' on. Keep an eye out for issues and maybe scan for pending codes in a few more days to be sure.

anyway, fingers crossed.