How does a noob liberty owner diagnose turbo issues?

[YungJulio]

Hey guys,
Recently I feel as if I may have lost power and in specific boost. Sometimes, when accelerating, it feels as if the turbo is not spoiling until very high RPMs. This is only sometimes and not all the time. Recently I have also started hearing a very quiet sound kinda like a police siren. It’s a very quiet whine but it’s there and you can hear it. I thought i might have a boost leak so I went to my mechanic but he told me you can hear a boost leak and assured me there isn’t a leak.

I’ve looked around on this forum, and tried to find answers before starting a new thread. Some recommendations include finding someone in my area with a. Tactrix or btSsm. I got in touch with Kelvin Krishna and was planning to meet Up with him. Other recommendations for similar problems was cleaning or replacing the banjo bolts and the avcs solenoid.

I really don’t want this to end up being a very expensive issue so if possible, I would appreciate expert opinion on how I should tackle this. Should I visit a mechanic? If so who in the Sydney area is recommended? If I go the Tactrix way, what exactly is it and is it sure to help me diagnose my issue?

P.s. I just got into my car as I just finished work and when I turned it on, I was hearing a very weird noise from the front of the engine bay kinda like an inconsistent buzzing or ‘static’ noise. It sounded like trying to find a radio channel but 100% it was from the engine bay. I gave it a slight rev and it fuked off. Pls help. Why are Subaru’s problem after problem?

Car is 2004 Subaru Liberty GT
No engine mods. Just slight suspension and brake mods.

[Yowie]

I feel as if I may have lost power and in specific boost. Sometimes, when accelerating, it feels as if the turbo is not spoiling until very high RPMs. This is only sometimes and not all the time. Recently I have also started hearing a very quiet sound kinda like a police siren. It’s a very quiet whine but it’s there and you can hear it

My poorly-rebuilt (unbalanced) VF46 turbo had a screechy-whine sound at the point I had it pulled out and sent for a proper rebuild. If your turbo hasn't been messed-with that issue seems unlikely for you though

[dr20t]

Could be many things but from what you’re describing my best narrowed down guesses (yes that’s the best anyone can do without inspecting the car) are:

1. Bad Pre-turbo exhaust leak - check up pipe to manifold connection, turbo to uppipe connection or crack in the turbine housing

2. Shot turbo -

I would strongly suggest checking it out asap because if it’s the second one above, this can cause more (larger and more expensive) issues (like blown motor due to metal getting into oil and killing a bearing

If it is the turbo, make sure you also check the banjo bolt filter on the avcs solenoid - this is a known culprit for failure / blockage and thus restricting oil to turbo which kills turbos

Good luck

Mick

[bigBADbenny]

Blown turbo diagnosis

I’d do some basic health checks eg inlet pressure test, check boost control hoses etc before eg removing dump or turbo inlet pipe to check for runout/damage on the compressor wheel or exhaust turbine.

Or remove intercooler to check for shavings in the compressor outlet. Check, clean and or replace the PCV whilst the intercooler is removed.

Maybe grab a new core for your turbo from kinugawa etc if it is blown, but confirm if the turbo oil supply and drain aren’t blocked.

Oil starvation will kill the new turbo in seconds.

Check if your car has turbo oil feed banjo bolt filters and remove if blocked.

The turbo oil feed banjo bolt is on the rear or top of the rhs head.
Banjo bolts that have filters for the turbo (and avcs system) are known to have a raised section on the bolt head aka a nipple.

A sharp tooth pick is useful for fishing for and pulling out the oil filters.

[bigBADbenny]

Basic checks.

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

Note the codes accurately.
If using a generic shop scan tool get long term fuel trims A-D and note the percentages.
If using Btssm or Romraider get a Learning View.

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 or listen for hissing.

1 inch of the end of a medium tuna can with masking tape wrapped around for fit is useful to block the inlet pipe post maf. A hole can be drilled eg with scissors to inset a rubber tyre valve along with some silicone or 3bond sealant.
If using breath or a pump with a one way valve, remove the schraeder valve with a tool or a small flat screwdriver.

Generally due to valves being open your inlet pressure test will be restricted to 1psi max, it’s best to use a regulator to 1psi if using a big compressor to avoid bursting pipes and cam seals. I use a little 12v tyre compressor which has a gauge and low cfm, it’s noisy so I turn it off to listen for leaks once the inlet tract has pressure.

I do the test with the key on acc to allow the throttle plate to open a little.

On GT’s it’s possible to remove the vacuum hose at the brake booster and blow breath or use compressed air (1-2 psi regulated) past the one way valve. Note the inlet pipe must be blocked, post maf.

From there add smoke to the air starting at 1psi, either way have a strong torch handy for inspection.

Bear in mind to continue the inlet pressure testing after each leak is found.

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 rubber 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 may recently had the in tank fuel filter or fuel pump changed, there’s also the possibility of an incorrect reinstallation, usually related to missing, pinched o-rings in the joins between the filter and pump cradle assy, 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 which alas was not applicable to all models.

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.


Inlet pressure test with smoke:

Get an old empty paint can, some garden hose, silicone caulking nozzles and a step drill.

The nozzles can work as low pressure fittings.

Tyre valves with the valve removed & bicycle pump hoses also work well.

Run 2 lengths of hose to and from the paint can lid.

Insert one end into air line, reg set to 1 psi.

Insert other end into bov ref hose.

Plug the short fat bit with a jam jar lid, it’s around 2” diameter iirc.

Get a rag with some oil on it, set it on fire so the oil smokes, or use a 12v vape element and fluid connected to your battery.

Drop the rag in the can whilst it’s smouldering and seal the lid.

Open reg, use a very strong torch to spot the smoke.

Do this and or use soapy water spray/bubbles.

Also listen for hissing.

Any hoses that get blow by (most of them) can rot from oil contamination, usually on the underside from oil pooling.

Or they can crack from being near a heat source eg the engine, so you really need to check them in a 360’ fashion.