Hey y'all,

I love my Fit (2011 5MT Sport w/ 188k mi), I've had it for around 6 months now, but it has an extremely annoying behavior when driving in traffic that has been driving me insane.
When I am rolling in gear off-throttle (pretty much any gear), and go to reapply throttle, the car kicks me into my seat. Almost no matter how gingerly or progressively I try to get on the throttle, it will happen.
Occasionally it only kicks once, but around half the time it will kick you in your seat multiple times like a spring. I've also sometimes recreated this feeling while going abruptly from low to high throttle. It will also sometimes happen when coming off-throttle: instead of one "kick" forward in your seat, it will kick a couple times. I know the car is designed to continue applying a little throttle after you let off the pedal for emissions reasons, this is probably what I feel when coming off-throttle. But I can't figure out why the car is so harsh when coming on throttle in gear.
It almost feels as though I have a bad engine mount, and the drivetrain is suddenly kicking into life once the slack in the drivetrain has been taken up. Here's the kicker though (no pun intended) -- I've replaced all three mounts already AND done the "window weld" mod on the torque arm, to no avail. I guess the best way to describe the feeling would be that -- it feels like there is some "slack" in the drivetrain that needs to be taken up when coming on throttle. There are NO mechanical clunks or noises accompanying this feeling -- it's all felt by the driver.

Here is what I HAVE done to the car since I got it:

- New plugs (cyl 4 was definitely leaking exhaust gases into the spark plug chamber, and previous owner had a history of replacing plugs and coils. I tightened all plugs to the newer, tighter torque along with anti-seize)
- Valve adjustment
- CDV delete and stainless clutch line (Sebs garage kit)
- All three engine mounts replaced (and window weld treatment on torque arm)
- Replaced clutch and flywheel with Exedy kit, OEM bearings and OEM lube
- Replaced trans oil with Honda OEM juice
- Passenger side driveaxle replaced with OEM unit under recall.

I also have issues with the smoothness of my clutch engagement. If I'm not extremely gradual and intentional coming off the clutch pedal, and I don't ace the right RPM, the car will usually kick much in the same way it does when coming on throttle while rolling in gear. Skill issue? Maybe. I've been driving manual for a few years now, my other car is a Miata, and I'm used to a much more forgiving drivetrain.
Is it possible that, at the end of the day, the Fit is an econobox and drivetrain harshness is inevitable? Maybe. This is the only manual Fit I've driven, so I have no basis for comparison. I'd love to know if you have the same feeling when driving your car around normally.

Here are my half-baked, non-mechanic theories of what could be going on:
- This is an innate consequence of the Fit being an econobox, and I have to accept it or get rid of the car;
- I've read people complaining about the throttle mapping in these cars, how Honda mapped most of the throttle % in the very first bit of the accelerator pedal travel to make the car feel more peppy. I'm not willing to spend hundreds of dollars on a Pedal Commander only to come out empty-handed if it doesn't fix the issue.
- Possibly the fuel system is gummed up and my injectors won't spray correctly at extremely low throttle, leading to an abrupt increase in fuel when coming on the accelerator (though I'd imagine this would trigger a CEL);
- Possibly my front struts are worn, though I can't imagine how this would translate into this type of drivetrain feeling. The car does not clunk over minor bumps, though it will thump in the front if I really hit a bump or dip into a manhole cover at speed.

Do y'all have any ideas of what I could look into next? I'd appreciate any and all opinions; this car can be really infuriating to drive in stop-and-go traffic, which is unfortunately most of my commute.
Sorry for the wall of text. I tried to exhaustively explain the circumstances, and I get a little verbose right after my morning coffee.

Thanks in advance!

 

My AT Fit did that after I replaced a part and didn't do an idle relearn. I don't remember which part, sadly... Car was really, really more peppy than usual, to the point where I was able to spin the wheels easily.

But once the relearn was done, everything went back to normal. Relearn was done by my mechanic with some kind of scanner tool.