H6 Throttle/DBW or MAF Issue

[Curley5959]

Hi All,

In the midst of having a tune completed, I am still having issues with lag and jerkiness. Noticed today it is also doing it on stock as well.

Symptoms
- Lag in 3rd gear - moderate acceleration - hesitates for a second or two - doesnt happen all of the time
- Jerkiness in 1/2/3/4 when taking foot off accelerator - worst place is town / traffic driving - foot off accelerator to slow down and it is jerky for 2-3 seconds - hard to drive smoothly.
- After flashing back to stock the other day after testing a tune, everything was fine but the next day I drove the RPM was surging up and down when coasting either in neutral or with the clutch in, around 10km or so - After another ECU Reset it has been fine.

It sounds like a DBW issue, so I have done a few things with no improvements, such as using contact cleaner on all electrical connectors/harnesses etc, especially the DBW and Accelerator, cleaned out Throttle Body with Throttle Body Cleaner.

Other things that have been done include Major Service 10,000km ago (spark plugs, all oils etc), Fuel Filter, Cleaned OCV Solenoids, New Denso Oxygen Sensors, Cleaned MAF, but nothing seems to work.

After an ECU reset the car seems to drive ok for a bit but reverts back to its jerky/laggy self after a while, making it difficult to do anything, do a reset, and test for results.

If I can determine exactly what it is, I will look at purchasing replacement parts. At this stage, I am thinking either MAF or the DBW system. Would anyone have any part numbers for these?

I have been trying to sort this out for around 4 months now. It is certainly doing my head in and I am completely out of ideas.

Any help is much appreciated.

Thanks,
Aaron

[HardwareBoB]

Vacuum leak.

[Curley5959]

Vacuum leak.

I completed a home made smoke test and fixed a crack in the airbox. Didn't find any other leaks but maybe need to have a proper test done.

I did have it booked in at a local mechanic a while ago who cancelled on me the day before. Their excuse "We don't have a smoke machine". Could have told me that the week prior when I booked it in..

Any obvious places I should check?