Massive shudder during 1st to 2nd gear change

[conandrews14]

Hi there. Newbie to this forum

I have a MY10 Liberty GT 2.5 Turbo automatic sedan that over the last couple of months has started exhibiting a very strange problem, so strange in fact that I have parked the car until I can get it repaired.

There does not appear to be any pattern under which this problem occurs, except that it occurs when the transmission changes from 1st to 2nd gear. It is completely random also and does not happen all the time.

When I take off from a standing start and the car revs out in 1st gear to the point it's due to change, the transmission momentarily (appears) to go into neutral and the car rev's quite high. After what appears like a split second, I experience this almighty shudder, something like being hit from behind at high speed, before the car continues in second gear. To say this is quite unsettling is an understatement, particularly for my wife that drives this car from time to time.

If anyone has any suggestion on what this could be and how I can get it fixed (affordably) I would love your feedback

Thanks in advance

[bigBADbenny]

You can preform basic checks, eg read plugs, confirm inlet tract vacuum pressure etc, perform maintenance eg flush atf, or you can attempt diagnosis via the obdii port which is usually a combination of reading DTC aka CEL codes, taking a learning view and logging relevant engine parameters.

Or take the car to a non dealership Subaru specialist for diagnosis.
It really depends on how much you’re willing to learn about your car or if you have the time to diy it even.

My guess is its an avcs issue, but it could be caused by a whole slew of issues. Very slowly vary the revs between 1200 & 2200 rpm in neutral, to see if you can provoke the avcs issue, if the engine starts shuddering and the revs hunt, there’s your issue... But check those parameters anyway during logging.

Let me know if the experts are stumped

[bigBADbenny]

This doesn’t cover transmission or driveline issues:

Basic checks.

Get the cars obdii port scanned with a scan tool to check for DTC’s aka CEL’s, both current and historic.

Google the codes with make, model and engine keywords.

DTC codes have diagnostic trees in your cars FSM, you can use this info to perform basic troubleshooting in conjunction with info on eg this forum.

Use a google site search with your relevant keywords to search. Eg:
“site:www.forum.liberty.asn.au keyword keywords”

In the google search bar.

More advanced logging and learning view can be done with BtSsm or Romraider.

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

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).

Pressure test inlet tract with smoke or dilute detergent bubbles from a trigger spray bottle.

The most basic inlet pressure test is to get someone to rev the car in neutral, whilst you spray the bov, tmic etc with soapy water, looking for air leaks as the car will boost from vacuum to 0psi.

From there, block off the entry of the short fat bit (post maf) and apply any type of low pressure (breath, bike pump etc) car off, spray soapy water.
From there add smoke to the air starting at 1psi, either way have a strong torch handy for inspection.

Also check if your fpr is hooked up to the lhs rear inlet manifold runner. Symptom: backfire and or stumbles under boost.

Gently cleaning the maf is a good idea, use crc maf cleaner on both the inlet temp sensor directly, and the maf wire indirectly via the adjacent air tube.
Be sure to carefully reseat the maf using a little grease to make sure the maf o ring is not pinched. Blow out or replace the air filter at the same time.

In addition to the stock turbo inlet pipe rotting due to accumulated blow by where it meets the turbo,
the stock intercooler to throttlebody pipe is a known issue due to its gasket design at the outlet to the throttlebody.
Inspect, use a quality t-bolt clamp/s eg murray or oetiker stepless, and preferably upgrade to a silicone TB hose eg AVO or Kobe.

Other basic sanity checks are related, visual inspection with a strong torch and inspection mirror of all head breather hoses, boost control and fuel purge hoses, their originating connections, joins and return to the turbo inlet pipe. With age and miles, these pipes and hoses can harden and crack, usually where the fault can’t be seen, eg on the lower side (gravity) or engine side (more heat).

Also if removing the top mount intercooler, pull the pcv at the rear of the inlet manifold, inspect, clean or replace it.

Since you recently had the in tank fuel filter changed, there’s also the possibility of an incorrect reinstallation, usually related to missing, pinched o-rings or not using double o-rings on an aftermarket fuel pump outlet.
If inspecting the bucket and filter assembly, be sure to check the loom connection plug on top of the assy for burnt or corroded pins.
This check would have also been performed during your recent recall/inspection.

H6
Get Btssm and log avcs and vvl angles, per cylinder misfires, neutral position and clutch sensors, make an LV as well.
Visually inspect the oil pressure sensor/s for leakage.
Pressure test inlet tract post maf for vacuum leaks.
Clean the maf, directly on the inlet temp sensor, indirectly for the maf wire, taking care not to pinch the o ring on reinstalling.
Blow out or replace the air filter at the same time.
Faulty brake lights or non resistor led tails can induce failsafe mode on some models, as can vdc issues related to the steering sensor in the clockspring.

H6 avcs & vvl:
Because just like gen4 turbo avcs and davcs,
H6 avcs and vvl are a self calibrating system using the crank and cam position sensors, plus the vvl oil pressure sensor.
Over time, the avcs solenoids get out of whack, the ecu tries to overdrive the lagging solenoid resulting in vvt angle oscillation or inactivity.
The vvl system is apparently more reliable but still subject to wear and tear especially as regards the dedicated oil pressure sensor adjacent the engine oil pressure sensor.
Thus logging is the key to verifying the fault if any.

[zapp87]

100% bet your valve body will need replacing. You may find the problem to be intermittent at the moment but it will become more frequent over time.

Check out this thread, few guys with the same issues (I sadly was one of them)
http://forum.liberty.asn.au/viewtopic.php?f=73&t=35044&start=30