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Old 10-12-2023, 05:24 AM   #1
mantekbhogal
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Member#: 535789
Join Date: Oct 2023
Post 2019 WRX knocking randomly

Hi everyone

I am new to NASIOC. I do need help with an ongoing issue with my 2019 WRX. I had crank bearing fail and got the engine rebuilt. Car is completely stock. During rebuilt i got king pmax bearings installed, new sparkplugs, new PCV, cleaned carbon deposit from the valves, used redline fully synthetic oil, etc.

After the first start, i felt some hesitation whilst driving. Anyhow, after the break-in period, the frequency of hesitation increased. The hesitation was random though but it felt like when giving gas, the car is not driving fast. Boost is going all the way. Did a smoke test, found no leaks. Got the first O2 sensor changed, same issue. And whenever I reset the ecu by disconnecting the battery, the car ran good for a while, but hesitation came back. Also installed thick 4 gauge ground cables from the alternator, but issue persisted.

For the longest time I kept on looking for answers, but couldn't find any solution. So I bought an accessport to log data but kept on stock tune. I noted the DAM keeps on dropping, even went to 0.188. And once it goes down, it never goes back to 1. DAM fluctuates, goes up and down but never 1 unless i reset the ecu. In the logs, there is knock readings getting registered mostly on cylinder 3 & 1. But the knocking intervals is random. Its like i register about 170-180 knock sums in 60kms of drive. I am not sure what is causing this knock because i have been using 91 octane gas from Costco. I have been using the same gas since i bought the car.

Not sure why the DAM is dropping and causing the ignition timing to pull. Please if someone can advise for the fix.
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Last edited by mantekbhogal; 10-16-2023 at 11:05 PM.
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Old 10-13-2023, 08:56 PM   #2
mantekbhogal
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Member#: 535789
Join Date: Oct 2023
Unhappy

attaching datalog: https://datazap.me/u/mantek-singh-bh...8&zoom=420-614

these graphs is me cruising at 100km/h with 10km/h increments. I notice, at 140km/h, engine only knocked 1 time but at other speeds, knocking is significant.


https://datazap.me/u/mantek-singh-bh...1&data=9-29-33

this graph shows that the DAM is dropped to zero.

Please help.
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Old 10-27-2023, 10:47 AM   #3
GoFrogs
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Member#: 507317
Join Date: Oct 2019
Chapter/Region: MAIC
Location: SW Ohio
Vehicle:
2019 WRX
Pure Red

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Quote:
Originally Posted by mantekbhogal View Post
I am not sure what is causing this knock because I have been using 91 octane gas from Costco.
Is there a different station you can buy 91 from, such as Shell, BP, Sinclair, Sunoco, Exxon, or other major label fuel brand?

Is there any gasoline above 91 in your area? Here in SW OH, we get 87, 89, and 93. There are some stations that have 91, but for the most part, everyone has 93 as the highest octane and skips the 91. Not sure why, but that's how they do it here.

If you can't get higher than 91, have you tried increasing the octane yourself through off-the-shelf bottles of various octane boosters? I do not know which one is "the best"; nor do I know what they mix ratios get you in terms of an octane rating, such as 100?, 104?, 110?, etc.

How "good" is Costco 91?
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