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Strange issues after engine rebuild
Hello everyone, I would add long time no see too 
So, I am currently facing a strange issue with my Citroen DS3 1.6 THP after a cylinder head rebuild that I personally did 1 month ago.
After I changed valve stem seals (due to exhaust smoking), cleaned valves, timing kit, replaced almost every seal that I found in front of me, upgraded silicone coolant hoses, viton turbine oil return hose, crankshaft-ac-alternator belt, VANOS sprocket, all necessary bolts tightened based on specs etc. and the car also started up and moved normally, I have to say that I am facing a pretty strange fuel pressure issue only when the car is idle.
So, sometimes (and not always) when the car is idle and if I press the gas pedal up to 2000 RPM, when the RPMs drop then I see a strange fuel pressure drop from 45 bar to 10(!!!) bar in my Torque app, the engine has a pretty obvious vibration like stalling and only when I press again the pedal to 2500-3000, the fuel pressure returns back to normal (45-50 bar).
During the start-up, the pressure seems normal around 48-50 bar and at WOT it's pretty solid around 120-125 bar without symptoms of leaning plus no fault codes (even on Lexia that I tested), no lights on dashboard...
Most importantly, this issue never appeared before the rebuild and I was wondering if something got affected even if I didn't touch the fuel system, except from the little high pressure fuel line which I replaced (against based on specs) and the fuel rail that I simply removed from the head without replacing or removing any injector from it. I was suspecting something at the new VANOS which is at the intake camshaft but I remember that it's properly tightened (pre-tightening to 20 N.m and then 180 degrees) and it was original part too. The most obvious culprit of course is the HPFP.
Just to add, the car is slightly tuned with hybrid turbo, intake, exhaust, remap, FMIC and uprated BOV.
Any kind of answer/opinion is more than welcome
So, I am currently facing a strange issue with my Citroen DS3 1.6 THP after a cylinder head rebuild that I personally did 1 month ago.
After I changed valve stem seals (due to exhaust smoking), cleaned valves, timing kit, replaced almost every seal that I found in front of me, upgraded silicone coolant hoses, viton turbine oil return hose, crankshaft-ac-alternator belt, VANOS sprocket, all necessary bolts tightened based on specs etc. and the car also started up and moved normally, I have to say that I am facing a pretty strange fuel pressure issue only when the car is idle.
So, sometimes (and not always) when the car is idle and if I press the gas pedal up to 2000 RPM, when the RPMs drop then I see a strange fuel pressure drop from 45 bar to 10(!!!) bar in my Torque app, the engine has a pretty obvious vibration like stalling and only when I press again the pedal to 2500-3000, the fuel pressure returns back to normal (45-50 bar).
During the start-up, the pressure seems normal around 48-50 bar and at WOT it's pretty solid around 120-125 bar without symptoms of leaning plus no fault codes (even on Lexia that I tested), no lights on dashboard...
Most importantly, this issue never appeared before the rebuild and I was wondering if something got affected even if I didn't touch the fuel system, except from the little high pressure fuel line which I replaced (against based on specs) and the fuel rail that I simply removed from the head without replacing or removing any injector from it. I was suspecting something at the new VANOS which is at the intake camshaft but I remember that it's properly tightened (pre-tightening to 20 N.m and then 180 degrees) and it was original part too. The most obvious culprit of course is the HPFP.
Just to add, the car is slightly tuned with hybrid turbo, intake, exhaust, remap, FMIC and uprated BOV.
Any kind of answer/opinion is more than welcome
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