bucking on steady throttle when warming up

[meisterjaeger]

Hi guys,

I've got an annoying problem with my car.

When the car is warming up and I'm on steady throttle, sometimes the car is bucking.



Bucking at 1:30min two times and at 1:35min one time.

The only abnormality I could find in the logs is the "dwell error".
In another thread Jadzwin discribed that there could be triggers issuses.

I don't know if it has something to do with the coils. I'm using VW single coil packs like these:

But the rest of the time, there is no problem with the coils. They work without any problem, still at 300kPa boost.

[WHPZach]

Your cam sync trigger tooth is alternating between 114 and 115. Post a scope log and your primary and secondary trigger settings.

[meisterjaeger]

Oh, I did not see that before. Thanks for the hint!



Hmm, may be a wiring problem or sensor broken?
What do you think?

[WHPZach]

You have the wrong trigger edge selected on one of your sensors. See how close your primary and secondary marks are on the scope log? The secondary signal should fall between two primary teeth.
If you've selected the wrong edge on the primary, you'll see ignition timing drift with RPM. Try selecting the other edge on the secondary trigger (you'll have to check and sync timing after making any changes).

[meisterjaeger]

Okay, thanks for the advice.
I will check that.
Compared to the manuel I thought the scope looks good.

If I change the trigger edge of the cam sensor to rising, the engine is not running.
So I will try to change the primary trigger edge.

[ren]

Good advice there.

FWIW I use those coils without issue.

[meisterjaeger]

Yes, there is no issue with the coils.
Yesterday I simply deactivated the cam sensor and changed from full sequential ignition to wasted spark.
And the engine is running fine without any problem.

At the weekend I will check the trigger edges.
I changed the trigger edge of the cam sensor, but with no luck. Engine won't run.
So I think it has to be the primary trigger edge.
I will post a scope log...

[RHD]

the crank trigger is correct otherwise the first signal after the missing tooth will be different spacing.

sometimes when the camsync edge is changed the firing sequence is one revolution different so try re-configuring your firing order, or enter an ignition output offset

Your cam sync trigger tooth is alternating between 114 and 115. Post a scope log and your primary and secondary trigger settings.

that should not matter should it??... when an engine has VVT the sync moves all over the place.

[meisterjaeger]

Just remembered of this thread and not to hide the solution.

Changed the China cam sensor against an 25 years old original Bosch sensor and everything is fine.
The trigger is no more altering between 114 and 115.
It stucks on 115 all the time.

Many thanks for the help and the discovery of the alternating trigger signal.