by bigBADbenny » Sat Oct 25, 2025 9:11 am
Use obdii to check the state of tune.
The primary indicators of tune health can be found in the FSM workshop manual warm idle specifications.
Generally:
Rpm 750-800-ish not surging
Afr 14.7
Boost (intake manifold relative pressure) -10.3psig at close to sea level (that’s vacuum btw)
Af1 learning (long term fuel trim) within +/-5%
Af1 correction (short term fuel trim) within +/-5% (note OEM spec is +/-10% but 5% is safer)
To gain more insight, use open source obdii with romraider or btssm learning view in which you’ll see knock correction versus rpm and load. More details can be found by searching this forum.
Warm idle is the engine running in closed loop fuelling, thus if it can run in spec in closed loop it will probably run well under load in open loop fuelling, however there are some potential exceptions which can be revealed using open source tools.
Obdii, displayed as virtual gauges on the iOS or android host device, fulfills the role of missing instruments in the stock car, namely a boost gauge, fuel trim etc which can inform how the engine is running in open and closed loop whilst driving both on and off load: specifically are you reaching maximum boost at wide open throttle: 15psi in S & S# and 7psi in i-mode.
In cruising on a flat road at freeway speed, ideally vacuum will be in the -7 to -9psi range or less, on my oil using 340kkm engine, -6psi was more likely.
If it’s running properly, within spec, knock under control, maintenance on point, then oil use might be the primary indicator for ultimately replacing the engine.
Once you’re using more than a liter of oil per tank of fuel (as was I) it might be time to consider a reco, rebuild or replacement.
Consider replacing the oil pickup tube with an aftermarket upgrade eg killer b, mine was almost cracked all the way.
FYI your car is a facelift my07 Gtb model regardless of its 2006 build date (like my car).
Using the correct description will help avoid possible confusion when looking for parts or seeking other assistance with your car.