loss of power while accelerating

[omer]

i have chevy trailblazer ext 2005 4.2 l L6 engine . there was head gasket issue before and my mechanic rebuild the engine completely with new pistons and lot of things after that i notice there is a problem when we are accelerating at 70 km/h to 80 km/h there is a power loss and i had to press the accelerator down so to get out of this hesitation , to find out this problem we went to some other mechanic and they told me to check the fuel pump and the filter . so we found that it was very bad and we cleaned it and after that it seems to be solved the issue 80% but i have some doubt still because there is a little bit hesitation but not like before and i noticed there is a gear changing on 70 km/h . is there any thing any one can help me in this please

Thank’s

Topic

[Darko]

I would start checking some basic stuff like compression of each cylinder and the fuel pressure. Is the CHECK engine light on? I would scan it even if it isn’t just to see if there is a pending code. Also you can check the ignition timing (you cannot adjust as it is controlled by the ECM but you can still check if it fires at the right angles).

[omer]

thanks a lot
i took my car to computer test and they told me there is no code you just need to change
1) ignition coils
2) fuel filter ( i cleaned and solved about 80% )
3) injector cleaning ( did it when rebuilding the engine)

regarding ignition coils i changed some with the old ones from junk yard because its so expensive to get all 6 coils because i am not sure it will work or not.
regarding the sensors i don’t have any code even i change the air temp sensor from junk yard.

[Author]

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