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Old 04-23-2020, 07:03 AM   #1
4NDY1980
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Member#: 513979
Join Date: Apr 2020
Default Low speed Pinging / Pinking / Spark Knock / Detonation

Ok so I've had 2 UK N/A 160bhp Hawkeye Impreza 2.0R Sports now, EJ204 engine, one 2006 and one 2007, both with roughly same mileage when bought around 70k miles. Replicas of STi/RB320 so with aftermarket exhaust back box or CAT back systems (not sure if that's relevant or not), other than exhaust and cosmetic mods i.e spoilers etc everything else is standard.

Both had exactly the same feel and drive and both developed this issue of pinking at low speeds and possibly hesitation (sometimes) (i think) or certainly the feeling of lack of power at times anyway.

I never got to the bottom of it with my first one and got rid eventually but now its happening with my current one. I can't say when it started happening with this one but i'm sure it wasn't happening when I got it, I've had it just over 12 months now and its on 81k miles.

Now before anyone jumps in with talk about valve chatter, rod knock, piston slap, heatshields, basically anything other than pinging/detonation... it's not that! I've done extensive research into those and pinging and i'm 99.9999999999% positive that is what the noise is. It doesn't happen on idle or revving the engine stationary. It doesn't happen when the engine is cold only when its fully up to temp and while driving. It happens on acceleration under load i.e. it's more prevalent on hills but can happen on level road at low rpm's (not too low!). It happens at low speeds when going back on the throttle after a gear change or slowing up for something and only happens for a second or so. It goes away with increased rpm's or engine speed. It reminds me of a diesel engine noise. Everything I've read describing it when it happens and how its sounds fits with whats happening. It happens less with higher octane fuel but still happens. I know a heat shield noise can tend to happen in those same circumstances but on both cars? the exact same noise in the exact same circumstances?? hmmm i think not and the heatshield has had plenty of attention recently so....

On my first R Sport I tried the following (not in order):

New Plugs (NGK Iridium)
New front o2 Sensor (Denso)
New in-tank fuel filter genuine
New EGR Valve genuine
New PCV Valve genuine
Seafoam clean through throttle body
Redex in petrol (not many though)
ECU Updates from Subaru (was already up to date)
Italian Tune-ups (Many)
No ECU fault codes
Knock Sensor genuine
New air filter
Cleaned MAF (sprayed with electrical contact cleaner)
Reset ECU many times
Oil and filter change (probably aftermarket filter)
Tried higher octane fuels and different brands inc vpower
Both Subaru and a local Subaru specialist couldn't find anything wrong with the car (Probably couldn't be arsed to to look into it if there is no fault codes tbh)
My current R Sport has had:

Plugs (same as above)
Front o2 (same as above) (had gone bad anyway)
Air filter genuine
Maf cleaned (same as above)
Checked banjo bolt filters on AVCS oil solenoids (no filters present)
Oil and filter change (Millers 5w30 Synth + aftermarket filter)
No ECU fault codes
Redex fuel cleaner, Wynns CAT and o2 sensor cleaner in fuel, Millers eco max boost in fuel
Higher octane fuels different brands (Pinging less but still present)
Italian Tune-ups
Neither car had the cambelt done (while I had them) and don't know if they had ever been done (no record but book stamps), both cars should run on 95 octane and always were run on 95 Esso fuel while i had them other than when experimenting with different fuels. Never supermarket fuel (while I had them), been under the bonnet that many times can't see anything a miss no sign of anything dodgy or hoses or anything air leaks etc nothing obvious.

As you can imagine, I'm at my witts end!... Got a vag-kkl cable coming this week hopefully and I have ECU explorer on laptop so will try logging when I can and post results but in the meantime, please can anyone shed any light on this?...

TIA
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