Fuel ? Air ? why does the power of the motor change ?

Hello !

I am having problems of power loss sometimes, car idles great and starts well. I have recently changed head gasket exhaust manifold, fuel filter and lot of other stuff. When i turn the key i hear the fuel pump to start also. But sometimes it just feels that the car doesnt have power as much it should. And sometimes it goes like crazy. I see a difference when going to same uphills. Sometimes i need to change gear and sometimes car even accelerates.

Any ideas suggestions ? It has the 1.8 2h engine with injection. Filters changed, sparkplugs looking good also.

i'm still new to the 1.8L engine, but i've got a similar problem. Mine is that the Frequency valve does not work, which means it lacks fuel when you need extra "umphh". When engine is warm you frequency valve should always "buzz" or feel like it's working (you can google the location of it, or you look near the end of your intake manifold - on the same side as the 5th injector, there is a valve with 2 hoses going to it, that's it). If motor is cold, you could unplug your O2 sensor, from what i know, it should start up the frequency valve (o2 sensor is a brown plug on the same side).

Other' than this… i'm assuming it's fuel issue. Make sure to clean out your intake flap