Pulsing when Accelerating

[kodyo]

Originally Posted by carma143

I don't typically go WOT when I don't want to. Only going up a steep hill have I sometimes pressed the throttle too quickly, resulting in this issue occurring. In a previous thread (when I thought it was the fault of the 87 octane gas) I commented how I almost crashed twice trying to cross a street at ~4 mph. It took ~6 seconds to cross the lane completely. Luckily I realized taking my foot off the throttle and back on allowed me to then exit at a quicker pace.

I have 1 friend who drives manual cars and motorcycles. He's a freshman at University of Colorado: Boulder. I asked him to drive my car and the first try he put on too much throttle, panicked and stalled. The next 4 tries he created the violent pulsing I've been talking about, followed by stalling. He quit after that, mutually agreeing so he wouldn't cause damage to my BRZ.

For any one else interested, I am planning to have the Subaru dealer test out the car to absolutely make sure this is normal, because it's preeeeeeeeeetty damn easy for this rocking to happen.

Maybe reset the ECU and see if it helps? IDK, it sounds sketchy, take it to the dealership IMO. Don't mention the 87 fuel thing...

[ImBatman]

Originally Posted by carma143

For any one else interested, I am planning to have the Subaru dealer test out the car to absolutely make sure this is normal, because it's preeeeeeeeeetty damn easy for this rocking to happen.

Does this happen all the time or only when you first start driving and the car is cold?

[carma143]

Originally Posted by Longhorn86

Does this happen all the time or only when you first start driving and the car is cold?

It can occur at any time, even after 30 minutes or so of driving. All I need to do is fully stop, then apply ~3/4 -WOT while treating the clutch pedal like normal, and it occurs, every time.

[SloS14]

75%-100% is a lot of damn throttle to be taking off from a stop unless maybe you're at the drag strip.

[Tenament05]

Originally Posted by Bergen23

It's nothing to be embarrassed about. When I first started driving stick, it'd happen every now and then to me. My dad would get in the drivers seat and he would drive it no problem. Then as more practice and conscious thought went into it, it happened less and less.

Plus, with a modern manual transmission, it's preeeeeeeeeetty damn hard for this rocking to happen

not really, considering deflection in stock bushings and how he is probably dumping the clutch too quickly, inducing/exacerbating oscillations. It's more than just the tranny that makes the car go into that seemingly-uncontrollable jerking.

[carma143]

Originally Posted by Tenament05

not really, considering deflection in stock bushings and how he is probably dumping the clutch too quickly, inducing/exacerbating oscillations. It's more than just the tranny that makes the car go into that seemingly-uncontrollable jerking.

Is a 1/3 of a second too short?

[Tenament05]

Originally Posted by carma143

Is a 1/3 of a second too short?

It depends on what speed your input shaft, output shaft, and car inertia/forces at work on the bushings & drivetrain. The exact aggregate forces are many and not easily quantifiable to "okay.. when the car is going 'x' speed, I should input 'x' action".. it's much more subtle.

Here's a hint, if you're staring at the RPM section, don't. Just try and feel the car out for a couple weeks. My WRX has an STI gauge that I bought 4-5 years ago on Ebay with a broken tach. I modded it to black that tachometer out, and those 4 years of driving improved my manual skills more than the previous 5-6 years by a longshot. It'll demand that you focus on feeling all these forces at work. Recommend you have a louder than stock exhaust though.

Peep the video of the faulty tach.. haha. oh man: https://www.facebook.com/video.php?v...33612798385582

And the end result:

[carma143]

Originally Posted by Tenament05

It depends on what speed your input shaft, output shaft, and car inertia/forces at work on the bushings & drivetrain. The exact aggregate forces are many and not easily quantifiable to "okay.. when the car is going 'x' speed, I should input 'x' action".. it's much more subtle.

Thanks. (Congrats! 86th post.)

[breadcrumbz]

This car has so much torque that you need to start in 2nd gear.

[carma143]

As a final update to this thread, I had Subaru Pacific over President's Day weekend take a look into the transmission, ECU, clutch, and gearbox while I was away. I told them that there might be an issue with an old software version for the ECU (my BRZ was bought within the first 2 months or so of release).

When I returned they had found no mechanical issue, but they had wiped the ECU and installed the current software version. The car felt slightly different, but the gear transitions were just about the same "jerkiness" that they were before.

Since then, just over a week later, my gear transitions have become incredibly smooth. I don't know if it's because I was skiing down Double Black Diamonds over in Big Bear for 4 days or the ECU software "learns" overtime, but my issues are gone, thankfully.

Now I can let women ride in my car without feeling embarrased. HUZZAH!
:happy anim:

[Tcoat]

Originally Posted by carma143

As a final update to this thread, I had Subaru Pacific over President's Day weekend take a look into the transmission, ECU, clutch, and gearbox while I was away. I told them that there might be an issue with an old software version for the ECU (my BRZ was bought within the first 2 months or so of release).

When I returned they had found no mechanical issue, but they had wiped the ECU and installed the current software version. The car felt slightly different, but the gear transitions were just about the same "jerkiness" that they were before.

Since then, just over a week later, my gear transitions have become incredibly smooth. I don't know if it's because I was skiing down Double Black Diamonds over in Big Bear for 4 days or the ECU software "learns" overtime, but my issues are gone, thankfully.

Now I can let women ride in my car without feeling embarrased. HUZZAH!
:happy anim:

The ECU does take a couple of hundred miles or so to relearn after a reset or flash.

[PandaSPUR]

I had this issue a lot when I first got my car.
Still get it once in a while.
Almost never get it anymore.

It must be the ECU learning how to drive.
Has nothing to do with this being my first MT car.

[De-bounce]

Guys lets keep more pages of this thread going. It's not the driver's fault, we all now must flash our cars to avoid this.

- _ -

[FRSGeek]

Wow, thought I crazy.

But as I accel. letting out the clutch or normal light acceleration it jerks. Just enough throttle variance to make the car bounce off the slop in the drive line and the rubber mounts. It gets into a harmonic effect almost.


Before anyone says, most of my cars have been manuals. What is different in this car vs. all others. Is fly by wire, computer controlled throttle. Just because my foot is on the peddle at 8% level to move while I let out the clutch. Doesn't mean the computer with all its inputs will output a constant TP or other adjustments it thinks it needs and the end result is dynamic acceleration leading to feeling this effect.