Hi Guys,
I know that there is many threads of loss of boost, but what i am facing is very strange.
I have Golf MK4 1.8T AWD engine code, not remapped. The mods I have are CAI, 007p DV. I already replaced all the vaccum hoses to Silicon ones, I deleted the PCV valve and I got a oil catch can, and I bypassed the N249 and removed the Vaccum reservoire.
I have a boost Gauge, and when the car is warming up from cold he needle is always between -15 to -20 HG, so i guess this is normal, and when I am driving the car it is between -22 to -28 HG so this is normal too.
When I accelerate on the 2nd gear the needle of the boost gauge go up to 8 ~9 psi at RPM 3000 but suddenly on RPM 4000 fall down to 4~5psi then go up to 7 than fall down, so it is not a stable curve that peak at 8~9 psi as a standard car and fall down slowly to 5 psi like it should do, it is not stable and it spikes up and down and the car loss boost from RPM 4000 to 5500 then you feel like the car is cutting off then it continues normally to 6500 before i change the gear to the 3rd.
In addition, on idle sometimes the needle read -20 HG but suddenly starts to go up and down with the RPM needle that is not stable, this happen sometimes. during traffic jam and not always.
what do you guys think is the problem? could it be a bad coil because i change the sparks 2 months ago or an oxygen sensor or the N75 valve.
you assistance is highly appreciated.
many thanks in advance,
Sas
