So monitoring tgv position should be possible with eg Romraider etc.
And thus a delete should also be possible.
Keeping the tgv’s as is, but deleting it all in the tune, tgvs open, would be considered a basic blind test of your theory.
That is if the issue persisted, you’d inspect tgv position physically to confirm the issue, presumably a stuck or lazy tgv.
I’m not sure if such an important to emissions motor could fail without throwing a cel/DTC tho.
ilib11 wrote:bigBADbenny, thank you for keeping an eye on this topic!
Re compression : Service Manual says - 142-171 psi, difference is 7 psi or less. My figures are slightly off these but the engine was not hot at the time of measurement.
so I got compression slightly below normal and the difference twice more than advised by the manual. Giving the engine is not new (160K), would these measured figures cause any concern from the practical point of view? What would real experience say? Like if I see one cylinder has a compression twice less then others that would definitely say there is a problem, would a slightly degraded compression be a concern? (note - engine has practically no oil consumption and does not require adding oil between changes)
Re vacuum: as per specs ( at least 19.7 in Hg on idle AC Off)
I noticed none of these conditions which also listed in the service manual:
1. Needle is steady but lower than standard value. This tendency becomes more evident as engine temperature rises +> Leakage around intake manifold gasket, or disconnected or damaged vacuum hose
2. Needle intermittently drops to position lower than standard value. => Leakage around cylinder
3. Needle drops suddenly and intermittently from standard value. => Sticky valve
4. When engine speed is gradually increased, needle begins to vibrate rapidly at certain speed, and then vibration increases as engine speed increases. => Weak or broken valve springs
5. Needle vibrates above and below standard value in narrow range. => Defective ignition system
Re gaskets - degradation of the composite gasket material: I got new sets, they either silicon ( TGV "binoculars" - Intake manifold ) or sort of a thin "cardboard material" ( cylinder head- TGV "binoculars" ), I thing you are talking about the "cardboard" ones. I tried to establish a leak there by using a lot of carb cleaner and /or butane gas - no leak found. SubiEvolution looked there too and did not find anything. So I think the only I can do next is to disassemble everything to get to these gaskets and replace them.
Re TGV: I have read people get these TGV removed and get simpler system and extra power, at least for previous years Subarus. I noticed the design is slightly different from the previous years - there is no separate TGV position sensor, looks like it is combined with the actuator now. Is that possible to remove TGVs for this 2010 model? Is that a common/recommended mod? ( I am thinking that if I need to disassemble the intake to check/fix gaskets, it may be good to remove these TGVs at the same time and save some effort).
Re TGV and idle: https://www.romraider.com/forum/topic360.html says that TGV could be related to idle:
Base Timing Idle (In-Gear) - This is the base timing in idle mode when the transmission is not in neutral. Although the map switching between A and B is not entirely understood, it appears to be related to the TGVs.
Base Timing Idle (Neutral) - This is the base timing in idle mode when the transmission is in neutral. Although the map switching between A and B is not entirely understood, it appears to be related to the TGVs.
As the original problem relates to idle , and especially is worse in gear ( a sort of load), I could thing this TGV lead is worth investigating.
P.S. Sorry for all these questions if there are too many of them.. I have to admit I am at the edge of my capabilities - I have no workshop so unable to lift a car, extract the engine from it etc. by myself. And the car has been in a reputable service with no obvious leaks/faults found. I simply would like to see a way forward from where I am now.
Kind regards,
ilib11
