Acceleration problems

[YCEE]

My car seems to have this acceleration problem sometimes where usually happens after driving for a while. Noticeable difference are sluggish acceleration, higher EGT, lower exhaust note, more air-flow readings from the S-AFC, and the BOV sounds louder. I have been told with all sorts of things like Boost leaking, Fuel Pump, Fuel Pressure Surge, blahblahblah...

However, there's this ECU reset thing I read and tried, and after I did this it will run fine for 500-1000km before it is back again. Can anyone please explain to me what the sh*t is going wrong?

(I am using standard ECU with AVCR and SAFC, stock turbo & intercooler, pod filters and Apexi NI exhaust.)

[zapf]

can't help here... but it sounds like one strange problem.

Zapf

[YCEE]

When this happens, I'll just have to shut off the engine for a while and start back on then it is gone.

Could it be the ECU retarding the timing? (Things like it is picking up knock, or high intake temp, water temp...) Anyway how does it feel like when the timing is retarded? Does it feel like boost is coming but there's flat acceleration?

[swampy]

Wastegate sticking open maybe??

[gtr33m]

Had the exact same problem, and thanks to Greg Jenkins, found the solution.

What you have is an over active knock sensor.

The problem probably cropped up after changing the timing belt, or cam gears or fiddling with the timing. Turn it up to high, then drive for a while and the knock sensor kicks in and drops your boost to keep you from damaging the engine. A good little safety feature, but it often fails or is over eager and kills you for no reason.

try checking your timing first, then setting it back a bit. If this fixes it, then leave it at that.

If it doesn't try the following. I haven't done it yet, but Greg has and it fixed his problem. Exerpt from his email:

I had the same problem in a GTST I had and it turned out to be the detonation sensors picking up detonation when it got hot and retarding the timing, it is easy to fix with a couple of 5c 560k resistors, cut the 2 leads going to the detonation sensors at the computer and wire in the resisors to earth so the computer still thinks the detonation sensors are there, because if you leave it open circuit the timing will be retarded all the time. There are 2 ignition maps on the chip and when detonation occurs it uses the second map with retarded timing, this problem also occurs because of the hot weather which makes the car more prone to detonation. I have the 2 resistors on my GTR and the gauge stays constantly at the same pressure. Anyway you will be able to hear it if is pinging if you get bad petrol. Try it I am sure it will fix your problem.

AND

There are two thick white wires on the harness/plug next to each other, one resistor connected to each one and run to earth, you must cut the wires so the detonation sensors are isolated.

Once again, credit to Greg for fixing this problem.

[YCEE]

Thanks! Will try to hold the timing back a little, mine is set at 21, maybe I should put it back to 20 or less.

Anyway, this explains it... When the knock sensor detects knock, it uses the second map until you turn off the key, and then it returns to the normal map? The second map is sh*t, it cause a higher EGT and uses a leaner mixture (probably because it is dropping boost also... ahh boost controller...)?