Hesitation when decelerating (SMG)

[x Spades x]

Hey Everyone,

I'm having an issue when downshifting. If I'm in higher rpms (+6k) and I down shift, the car blips the throttle (let's saying 7.5k) and starts engine braking. Now at this point I feel like everything is fine, but all of a sudden i feel like car lurch forward like the clutch disengages (and the car is free rolling)... then it reengages and continues to engine brake... then disengage.. then reengages again.

Its very jarring and it only seems to happen in 3rd gear.

Has anyone ever experienced this?

Thanks,
Kareem

[sapote]

Clutch disengagement or DME injecting more fuel?
During engine braking Dme supposed to cut off injectors based on rpm, TP sensor, clutch switch and GPS, but if the signals don’t make sense it could resume injecting to avoid stalling .

I would add a fuel pump cut off switch to turn off the pump during engine braking and see who doing what.

[x Spades x]

Clutch disengagement or DME injecting more fuel?
During engine braking Dme supposed to cut off injectors based on rpm, TP sensor, clutch switch and GPS, but if the signals don’t make sense it could resume injecting to avoid stalling .

I would add a fuel pump cut off switch to turn off the pump during engine braking and see who doing what.

Hmmm... could it be a TP sensor issue? I feel like that would be the easiest one to tackle first, no?

[sapote]

When it lurked forward, if the rpm dropped then the clutch disengaged, and if rpm shot up then DME enabled the injectors again.

[x Spades x]

When it lurked forward, if the rpm dropped then the clutch disengaged, and if rpm shot up then DME enabled the injectors again.

Understood.

It was definitely more the first one.

I just went for a drive and 3rd gear has officially left the building. All other gears shift fine so id imagine it's the GPS

[sapote]

But why the GPS acted up only during a hard engine braking?

[x Spades x]

But why the GPS acted up only during a hard engine braking?

Well I was thinking GPS just because I totally lost 3rd gear yesterday. The car has been sitting overnight, and 3rd is now back. I'm at a loss

[sapote]

Well I was thinking GPS just because I totally lost 3rd gear yesterday. The car has been sitting overnight, and 3rd is now back. I'm at a loss

I missed this part. So it is not just clutch disengaging/engaging issue during hard engine braking.
SMG actually don't have GPS, but the TCM uses the same encoder on the tail shift actuator to detect gears and neutral positions, and I don't think the encoder issue causing 3rd popped out.
It's time to remove the detent/roller pin on the upper left side of tranny and check for fracture/wear. It's at the same place for GPS on manual box.

[x Spades x]

I missed this part. So it is not just clutch disengaging/engaging issue during hard engine braking.
SMG actually don't have GPS, but the TCM uses the same encoder on the tail shift actuator to detect gears and neutral positions, and I don't think the encoder issue causing 3rd popped out.
It's time to remove the detent/roller pin on the upper left side of tranny and check for fracture/wear. It's at the same place for GPS on manual box.

Does this require dropping the tranny?

[sapote]

Does this require dropping the tranny?

You can try to lower it down and see if the part can be reached. I think it's possible without removing it off the car.