[studio54]

Hello,

I noticed something relatively new on my car since my turbos were replaced, and i would like to troubleshoot it with you guys.

I will try to describe the best as i can :

When cruising at low speeds in traffic or slow situation, for example :
- 1st gear at 20 kph or 2nd gear at 35-40 kph
- something between 1500 & 2000 rpms
- not in boost
- no codes

Car is a 6MT.

Only keeping my slow speed steady with the throttle pedal, if if let off (even gently), it will bounce more than it should, it don't know how to describe it really well but it's like a kind of bounce of engine braking or like if was releasing the clutch too fast (but i am not touching it i am already rolling), it makes no particular noise, just a bouncy buck, back and forward, passenger can feel it.

It's not a sharp jerk, it's a round jerk (if this have sense?).

If i apply a bit more throttle from steady speed, like going from 30kph to 40kph and let off, the bounce will be more pronounced, it looks like it bounce with the very low end torque.

I would say the bounce happens almost immedialty after let off.

If i am driving faster, in higher rpm like more than 2500rpms, it doesn't happen.

If i spirited drive, no shake or vibrations or something, it WOT just like normal, and high rpm let off doesn't bounce.

I don't think it's a misfire cause it's not shaking the same way (i had one bad coil in the past, it was shaking and the feeling was different + i got codes)

Is it possibly a symptom of bad motor mounts ? related to the recent turbo install ? cause subframe was dropped, maybe something had not been reinstalled correctly ? (bad motor mounts are supposed to be messy at all rpm ?? or could it be only felt in low rpm?)

Transmission mount ?

Is there tips to know if it's mounts related ? tests i can do on the road?

Or could it be engine related ? tune ? (but i almost use MHD V7 all the time, prior turbo install i didn't have this bounce)

O2 sensors ? (i don't know if it's possible simple, but for the record, after one of my turbos blew, the old o2 sensors were reinstalled)

I will try to catch it on a log if it can help.

BTW should i reset some adaptations ?

Thanks for reading my long post. If something else came back in my mind, i will update.

Any hints appreciated

[Brandoch]

Do you have burbles turned on? I noticed on my car with burbles on, its more jerky than without.

[Recoiletiquette]

I would also like to get to the bottom of this problem. I've been having the same issue the past 2 weeks with my car. And its exactly how you described i fills like I dumped the clutch but im already about 10-15% on the throttle and moving from 10 to 20 MPH when it does it. Only happens in 1st and 2nd gear that I can notice. I turned my burbel off to see but that was the problem but it didint change much. Really it felt worse, but without the burbel it felt like it was very aggressive engine breaking but this is problem is different it fills clutch related.

[studio54]

Nop, burbles are turned off.

A thing i forgot to mention but i don't know if it could be related and worth to be mentionned: my secondaries cat were gutted during the turbo install (because one of them was full of oil).
The exhaust path is not straight with two hollowed/gutted chamber but i wouldn't expect this behaviour at such low rpm, maybe i am wrong ?


Recoiletiquette

it happened for you with no change in the hardware ? no new parts or install ?

[Recoiletiquette]

Ya I have changed nothing on my car. I've been ruining same tune (stage 2+ 91 oct V9) no new or different parts. No new gas station. Nothing that I can think of. The only change I have that I can think of is the cold weather here. It has seem to come out of no where. And just fills like im dumping the clutch without enough throttle. But im already fully off the clutch and driving down the road. Its very strange. I've been catless for years now and haven't has this come up so im not seeing that being the issue. Its almost as if the clutch isn't fully engaged when i let off all the way, and fully engages on its own at a certain speed or or rpm. And like u said I've had plenty of miss fire issues with this car ( lpfp, hpfp, plugs, coils) so it didint fill like any sort of fueling issue. I just fully assumed it was a clutch problem cuz thats how it felt to me.

[studio54]

Ok, stage 2+ too, on 91 oct too ( ).

I will try to catch this on a log, to see if some values can explain this.

I can't remember exactly if the RPM needle is fluctuating when it does occur, but i don't think so, i will try to watch this next time i take the car.

Eventually try to log it, so we can compare.

[Recoiletiquette]

Ok sounds good. Ya I cant remember if rmp bounced ether. But if I even give it a bit of extra throttle it ether happens so fast I dont notice or it dont do it at all. But I will try to catch it in a log to see if anything is fluctuating.