600 RPM drop

[Serflex]

Hi,

Looking for opinions on what the cause of the issue I am having might be. No check engine light.

Vehicle: 2006 Legacy Spec.B, JDM Automatic. 2.0L

Basically, often when reaching higher RPMs the car will 'miss a beat'. It loses power for a fraction of a second, then continues to rise through the RPMs fine. This usually happens at higher speeds, e.g. when quickly going from 80KM/h (50mph) to 120 KM/h (75mph).

Images of the issue: https://imgur.com/a/cP5aPgt

I've had the car for about a year now, this problem only began in the last 2 months or so.

I purchased a data logging device, I'll attach a csv file if that can assist anyone with diagnosing.

I'm a complete novice when it comes to working on cars. As far as I know, my car is stock aside from having it tuned to 91.

Looking at the data, fuel being sent to the engine all but stops for a moment - then quickly resumes?

Cheers

 

tuner_log_22-10-14_2019.csv

[Max Capacity]

I'm not good at reading logs, but I would make sure the wires powering the fuel pump is good. I recall post about wire issues for some people.

 

Maybe check the sticky's you may find it.

[Max Capacity]

 

Not sure that will help but it maybe a start.

[snow05gtRI]

Could it just be the torque converter unlocking and locking again?  I used to see my RPMs dip and re-rise on WOT pulls in data logs and through discussing with my tuner, we came to the conclusion it was that.

I never really felt a power loss, though.  Could just see the RPMs dip.

[Serflex]

Don't think so, I tracked that and it seems all good. https://imgur.com/a/tDlP5hj

 

I added Spark timing to the tracking, here are the results: https://imgur.com/a/y2n7Ocs

Looks like the spark fails before fuel is cut?

Edited November 3, 2022 by Serflex

[m sprank]

Your IAM is 0.56.  If it is below 1.0 your car is F'd.  You sir have far bigger problems.  When your tune calls for 10 degrees of advanced timing, you get 5.6 degrees.  The car will not make proper boost, timing or fueling as it is in LIMP mode. 

[Serflex]

On 11/9/2022 at 8:49 AM, m sprank said:

Your IAM is 0.56.  If it is below 1.0 your car is F'd.  You sir have far bigger problems.  When your tune calls for 10 degrees of advanced timing, you get 5.6 degrees.  The car will not make proper boost, timing or fueling as it is in LIMP mode. 

Any ideas what can cause this, or how to go about fixing it?

[m sprank]

If your IAM is below 1.0 the most likely cause is knock.  What fuel are you using? If tune is jdm chances are its for 95oct.  

Re-read op. So its tuned for 91, I assume you are using at least 91 and the problem is new.  Well, you have knock.  Bad gas?  Bad bearings?  Noisey/loose component that the knock sensor is picking up? Is it real or false?  Must find the knock. A LV might help.

Edited November 16, 2022 by m sprank