i try to describe it as simple as possible but there were several steps, unfortunately.
It started with me building an open K&N. I connected the breather upstream in front of the MAF sensor, just like in the original.
I was very happy with the performance. But after a longer ride to Italy the dropouts started. I had a spare MAF sensor with me and exchanged it. Then the car drove well again for 300 km. But the problems started again on the way back and got worse and worse. In the end I could hardly hold the gas. The car only drove if I kept on moving the gas pedal.
I was back from my trip to Italy I hardly made it back home.
OBD2 could not really help. I saw the throttle close in the OBD. I changed the throttle but the symptom remained. So the throttle is ok but it is closed by the ECU, perhaps...or caused by a faulty plug connection...see below.
Then I swapped the throttle pedal for a similar used one. The car drove very well again. That was the time I posted it on TM.
But after a longer drive the error was back. I exchanged again the MAF sensor against a third one which I had on hand. The error remained. I drove this in the limp home mode without connected MAF sensor and without O2. sensor and without VCT. But even now the error remained and the throttle was disrupted.
I then have installed my original air filter box last year in end of May or June. Since then the car has been driving absolutely faultlessly for 6.000 km in 10 months.
Sorry I didn't report this on TM because I wanted to make sure that everything is permanently good. This is the case now.
(The only change from the original is that I left out the sponge on the breather intake and I mean the engine has more torque. I will clean the sponge very well and use it again in the future to test the difference again. But that is another story).
So I can not say exactly what the reason is re the drop outs.
Guess: 1) the MAF sensor became too hot due to the very close upstream mounted breather. But against this is the fact that the car also had the dropouts in limp home mode without MAF input.
2) The mixture was perhaps too lean with the open K&N and the ECU intervened.
3) I had changed the electric throttle but I had not paid attention to the throttle plug. When I later rebuilt everything back to the original (air filter box) I checked the plug of the throttle valve again and cleaned it. I even disconnected the red inner plug and preloaded all contacts a bit more. Since then the throttle response feels somehow more direct and spontaneous and I have no more dropouts. This contact is in an area where rain or washing water can reach into this plug.
Because I had changed so much I can not tell the exact reason. But my first guess is that it was this throttle plug.
To know for sure I would have to put everything back with the open K&N and also the original gas pedal to see that everything is still good. But that's a tinkering for some day. My car drives very well.
Conclusion, I would first check the connectors of the throttle and the MAF sensor (but the MAF connector is secondary because the error was also in limp home mode).
If you read with OBD2 it might show you a completely different error than I had...who knows.
BTW, Stuart, do you use the original filter box or an open system?
