Hi guys
For a long time now I've had a surging problem in my Spec B. Had the car to a load of different mechanics and no one has been able to offer any guidance. It has spent literally months away having every possible sensor and electrical part swapped out with no change.
Tonight, I think I've finally figured it out. The variable lift solenoid isn't being told to actuate when it should. Physically the AVLS seems to be working correctly because it always kicks in over 4000 RPM, but between 2000 and 4000 it should kick in based on a bunch of parameters which loosely seems to translate to how much you want to hoon.
Attached is a screenshot of some logging. The first column is of a shift from 2nd to 3rd, the red part is just when I shifted into third gear and went WOT, but AVLS mode is 1 (low lift/duration) for a period of time while at WOT then switches to 3 (high lift/duration) and I get the surge. The second column is of me stomping on the throttle in third, not such problem there, the AVLS goes straight to 3 even at only 2200 rpm. There is no annoying surge in this circumstance because AVLS engages and I'm still putting my foot down. The higher the load (going up a hill, in 5th, changing gear etc) the more likely I'm going to get the lag and surge.
I've had an XRT tune, well currently in progress in fact, and Ed isn't aware of the problem so I don't think it's typical of these cars. It's actually bloody annoying to drive like this because you never know when AVLS is going to kick in because it's always at a different time. And the power comes on strong and suddenly, the car squats and I probably look like a moron.
One thing Ed brought to my attention in the logging is that in pulls the RPM generally counts up but every few log points it there will be a value lower than the last. My first guess of what would cause this is a failing DMF, and I do have a wee bit of clutch shudder and harshness if I'm sloppy with changes. The car is also very jerky and shunty at low RPM and driving in car parks is difficult. If the engine RPM is fluctuating even very slightly because the DMF is stuffed then one would think that perhaps the load isn't being calculated correctly and that is possibly much of the reason why the lag is so bad after a shift.
My car is actually JDM but Ed convinced me to flash an ADM ROM but the problem was still there.
Anyone seen this before? Can anyone give any ideas as to what might cause the AVLS to misbehave like this?
This has been ongoing for over 6 months and I would really love to get this problem resolved! Thanks!