AVCS VVT angle out of sync diagnosis MY07 GT B

[cynner]

How close to do the right and left OCV's need to match up on the logs? Absolutely identical, or is it common that sometimes one will lag slightly behind the other occasionally (but mostly identical). And the issue where when cruising, one OCV oscillates in the logs (while the other is stationary) - mine only does that occasionally (was fine today... but yesterday was doing it a little). I'm just trying to work if my OCV's are in urgent need of replacing, or not bad enough to worry about for now?

[bigBADbenny]

Its up to you, it doesn't appear to be fatal, but the car will behave more consistently if they're both working properly.

[KiDo_Tuning]

The other symptom is intermittent boost spikes as the cams varying by 6 degrees while the engine is running is the same as the timing belt being off a tooth on one side etc

[cynner]

Hmm ok, so probably best to act on the early warning signs now... rather than after it becomes fatal.

Was there ever a consensus as to why a custom tune can cause the AVCS issue to cause more significant problems? Just unlucky coincidences? Or is the drive-by-wire lag in the stock maps more forgiving towards sluggish OCV's?

Kim

[KiDo_Tuning]

Hmm ok, so probably best to act on the early warning signs now... rather than after it becomes fatal.

Was there ever a consensus as to why a custom tune can cause the AVCS issue to cause more significant problems? Just unlucky coincidences? Or is the drive-by-wire lag in the stock maps more forgiving towards sluggish OCV's?

Kim

Stock tune runs so rich on fuel it is sluggish already, you dont feel it as much when you want smooth power

[cynner]

Cleaned the RH side OCV last night (although didn't use the 9v battery to actuate it - I'll have to give that a shot).

Here's a new log. Slightly better perhaps... although the RH side still lags a fraction behind the LH side (I am guessing that is not normal?). I'd be curious to see a log from a good car to compare...

Kim

Screen Shot 2013-08-27 at 7.59.28 AM.png (56.87 KiB) Viewed 4916 times

[bigBADbenny]

Looks lots better but not perfect. I think logging 6th at 100kph should give a better indication.

Did you reset the ECU?
Do it with the car warm.
Log the angles on restart with the clutch in and in gear.
Key off.
Key on.
You should see the VVT angle recalibration process on the second key-on after ecu reset.

[cynner]

Ahh nope, didn't do any re-calibration or ECU reset.

Will do that at lunch today.

What do you mean by logging the angles with the clutch in? Doesn't pushing the clutch in drop the VVT angles to 0?

[bigBADbenny]

From research, VVT angle is activated if the car is in gear.
So if you cant be stuffed going for a drive/finding a freeway etc. just follow the instructions above, and log 30 sec or a minute at 1500, 2000, 3000 rpm, in gear with the clutch in.
This approximates the first part of the factory diagnostic procedure which is a static test. Part 2 is a driving test iirc.
I've added 1500 rpm because this is where I was experiencing the off-idle shuddering/oscillation.

[cynner]

Ahh, awesome - thanks!

[Manaz]

Just logged my car.

Well, I thought I did. ROMraider was showing speed, rpm and VVT advance angle (left and right) in the logging window - but only time and rpm made it into the CSV file.

What a pain.

[cynner]

An ECU reset seems to have helped a bit (on the ECUdatascan the graph seems to match up pretty smoothly. The RH side lags slightly behind if the car has been idle for a second, but catches up to the LH side fairly quickly.

Here's a log in 6th... not sure why the revs are all over the place? Maybe that's just the ECUdataScan logging... (you'll need to scroll down to the bottom of the attachment).

Every now and then either the RH or LH drops up or down 1 degree of timing then corrects itself. No more oscillating though...

Do you think it's still worth replacing both OCVs?

Screen Shot 2013-08-27 at 2.41.06 PM.png (53.71 KiB) Viewed 4899 times

[bass_straitener]

I think you still have a problem.

That saw tooth looking graph shows an oscillating type issue on the right hand side.

[cynner]

Hmm, yeah. Although the oscillating was much more clear (like a wave up and down) before. I thought maybe the saw-tooth look was the ECUdataScan rounding up/rounding down the angle when it's just between two figures (eg: 14.51 degrees would display 15, and 14.49 would display 14). Not sure for certain though...

Would love to see some graphs of what it should look like...

[bigBADbenny]

Just a bit tighter than the other one you posted, less lag.
I'd do the freeway log at 100kph in 4th 5th & 6th to be sure.

Did you log the recal and the static test?

Pm me your logs!