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Old 01-30-2021, 11:56 AM   #11
jimmy12345678
Scooby Newbie
 
Member#: 516695
Join Date: Jul 2020
Vehicle:
2008 Impreza 2.5i

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Quote:
Originally Posted by Elbert Bass View Post
Sure it' not just a heat shield on the exhaust?
Based on the other things you looked at we are back to spark knock. If it happens under load/acceleration that is most likely spark knock. Primary cause for that is air/fuel going lean. I understand you fixation on valves but if you had a problem in the valve train it would most likely happen at all times.
Do you have the capability to see real time fuel trims? Be curious to see what they are cruising at operating temperature as well as the A/F sensor and O2 sensor under load. also check fuel pressure. Have you tried unplugging the MAF and driving it? Does it still happen?
Yes I do have an Autel MS906 scan tool and am capable of getting the live data readings, so I will check short and long term fuel trims, A/F and O2 sensor readings, MAF values, etc. while recreating the problem, as well as i-AVLS Duty Cycle and whether the solenoid is open or closed. Any other data PID's you feel would be handy to monitor?

I found something that COULD explain my issue in another thread on this site, tell me if this makes sense to you or if it's gibberish:

Quote:
Originally Posted by MSR View Post
The issue is the avcs gears, log the AVCS timing below 2k, see they float around off targets, gears seals inside are leaking to the wrong side, solenoids keep chasing targets, need to replace the avcs gears and also solenoids burnout chasing it.
This would also explain my "rattle" at high RPM's like that and should be able to be seen by a scan tool but might not set a MIL. When the "rattling" noise was occurring one of the times and I really got on it going up a steep hill, the MIL came on and set the P0028 code.

I've checked all the heat shields on the vehicle and none are loose or rubbing on anything (been burned by loose heat shields before on customer's vehicles) along with the P0028 code setting during the noise occurring makes me certain is it a legitimate problem.

Have not tried driving with the MAF unplugged, what exactly would it mean if the problem went away with the MAF unplugged?

I WILL get to the bottom of what is causing this issue, I might not be the best diagnostic tech but I'm stubborn enough to not give up when there's a problem LOL
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