Strange one indeed. Partially blocked back box or cat maybe? It might be gas escaping through a blockage of some sort.
Also, the engine management will probably go into closed loop mode at around 2k rpm and above meaning the mixture control is supplemented by information from the Lambda sensor. It could be that a faulty sensor would send the engine excessively lean or rich at this point, however, it wouldn't do so on full throttle, just light throttle, and it would almost certainly continue to show a fault as this is easily detected in the ECU. I wonder if the ECU stores a fault history? Might be worth getting it checked for fault codes.
Could it be a leaky / disconnected vacuum line to one of the dual ram actuators that is hissing? It would come from the front of the car, of course, but maybe the hissing sound is actually from there? This would have the double whammy of affecting engine performance due to incorrect positions of the dual ram valves and also introducing a (small) unmetered air leak into the induction system. I think the dual ram actuator at the rear of the plenum changes state just off idle (from open to closed).
I don't suppose it's the fuel pump making the noise? If this is on its' way out it may be that it's causing fuel starvation as the manifold depression decreases on an open throttle and fuel pressure has to increase to compensate? Could equally be a blocked filter, fuel line or in-tank pre-filter.
All just wild stab-in-the-dark guesses though I'm afraid.
Kevin
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Topic: poorly car loss of power (Read 1615 times)