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Old 07-05-2019, 07:35 PM   #4
bigBADbenny
Scooby Newbie
 
Member#: 314324
Join Date: Mar 2012
Chapter/Region: International
Location: Collingwood, Victoria, Aus
Vehicle:
MY07 Lib GTB 6MT Wag
OBP

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Here’s my incrementally updated avcs diagnosis guide: logging is the key.

Avcs checks.

Log avcs vvt left and right angles with Btssm or Romraider at 1700-2000rpm in neutral and in gear on the freeway, look for vvt angle oscillation, lag or inactivity.

My theory is that slight differences in the left and right avcs oil feed pressures, combined with the self calibrating nature of the avcs system cause one side, usually the LHS, to become overdriven and eventually fail.

The beginnings of this failure is seen as left to right angle lag.

The intermediate stage is one side wildly oscillating whilst the other side operates correctly.

The terminal stage is one side becomes inactive at which point the avcs system deactivates completely.

All stages can be encountered without triggering a cel.

My solution is to start with two new avcs solenoids and then to periodically swap them side to side (eg at 50k mi) or when significant angle lag becomes noticeable in logging.

If either issue is revealed, swap avcs oil control solenoid side to side to see if the issue follows the affected solenoid.
If so, replace both ocv solenoids.

If the issue doesn’t follow, check the ocv oil supply banjo bolts for blocked screens. The filters can be very deep in the banjo bolt hole and or broken up. Use a sharp toothpick to fish them out.

Very rarely, an avcs cam gear may be jammed with debris, or via incorrect installation, usually in this instance it will be locked at a particular angle as revealed by logging.

Go for the easiest tests (logging) first, if all results are negative, eg you have avcs inactivity which does NOT follow the OCV side to side swap, pull the crank and cam sensors to check for contamination by metal particles on the sensor face or check for oil supply issues at the banjo bolt filters.

For dual avcs prefl 2.0t, check if the exhaust avcs solenoids are leaking, the loom can suck oil all the way back to the ecu plug, causing multiple issues.

Log per cylinder misfires.
If misfiring, check spark plug condition and swap around coil pack on the affected cylinder to check if the fault is cylinder or coil pack related, or coil pack loom plug related (usually broken plug clip).

Get an LV (learning view) whilst you’re at it.
LV will reveal inlet leaks, IAM (low IAM = failsafe mode).
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Last edited by bigBADbenny; 07-05-2019 at 07:52 PM.
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