Hmm.. what gives your car air/fuel.... well.. the fuel rail gives you fuel..that is sent through a fuel pressure regulating valve... and that gets its fuel from the pump... which also passes through a few check valves.. as for the air.. I am not exactly sure about your make and model.. but in general there is a intake valve.. butterfly valve that opens on start to give your engine air... and your idel control valve.. which keeps the right about of pressure inside of your intake manifold with imput to your valve to increase or desrease pressure... this also then ties into your fuel pressure regulating valve.. which is operated with intake mainifold pressure. As for fuel mapping.. that is all does by your ECU... which is a OBD-I system..
When the car is cold (early morning, and late night) if I give it any push above 2k rpm it gives this weird sound, as if the engine is not getting petrol and/or air in a smooth way (i.e. as if there is a valve that is opening and closing randomly).
Then after 10 to 30 min. (randomly everyday) it becomes perfectly fine as long as it is hot... and it comes back after complete cool down.
This again happens in an increasing manner, i.e. everyday it becomes worse and it takes longer to stabilize.
I tried 3 times to change the air/rpm choke (as they call it here) (which probably is the butterfly valve) with a second hand one... the problem goes for one or two days and it comes back again....
The recent thing I noticed, is that I start the car (cold start) and it is perfectly fine, and the problem happens 2-3 min. after....
Really weird, but I feel it's related to a faulty piece that is kinda half functioning.
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