Roojai

I have found (on my trips on the autobahn in Germany of course), that it is very difficult to cruise above 85mph, as at a certain throttle position and engine speed I get knock link activity..
It is kinda like lift-off det or transitional det, and it occurs when the engine speed is above 4000rpm, the boost is -10 to 0, and I am on about 1/3 throttle.
If I lift of the throttle a tiny fraction then it goes away, but car can only travel at about 80-85 mph in this throttle position, or if I open the throttle a bit it also goes away, but then car accelerates to 100 mph and beyond, which is not what I want.
Any ideas as to cause and cure?

Roojai

any ideas at all?

ScoobyDuck

iTrader: (1)

what MY ?
it wouldnt be lift off or transitional DET, as youre not doing either.

sounds like its just running outa spark, or its getting a crappy signal from a position sensor (cam or crank)

if its got coil packs, then it could be a duff one, which would cause a missfire and thus your simptoms.
if the plugs are ok, try reducing the gap to 0.6mm and see what happens.

does it occur under any heavy load in lower gears?

humm, just read your post again - could be something like a split / leaking hose that causes air in to make it lean ... not easy that one. try the plugs tho

Steve

Roojai

Cheers for the reply, didn't think anyone was going to for a while there.

I am pretty convinced it is running a bit lean under those conditions. I don't think there are any splits in any of the piping. My AFR meter shows proper (rich) air-fuel ratios when on boost.

Spark plugs are quite new and gapped at 0.7mm and the coil packs are pretty new too.

I like the sensor idea, perhaps throttle sensor, my accelerater pedal does have a lot of play in it, I have to depress it about 1 cm before throttle opens. But then again the sensor for the throttle is at the throttle body, not at the pedal.

Ah well, something elso to fix, I would be bored otherwise eh

Heavy load in lower gears is fine. Car runs perfectly, except at a cruise above 85mph (or a bit slower than that in fourth).

The knocklink gives me one or two greens, and the occasional orange, just sparking up and down very rapidly, usually when the car is slowing from say 90 to 85, with 1/3 throttle open.