hello.i have a problem with my car for a year now.when i start the car in the morning after is sitting for 12hours it starts fine but after 5 second it has rough idle like a misfire and sometimes is backfire to the air intake.i have replace vanos solenoids both,thermostart,map sensor,cyinder head cover,spark plugs,check the timing,fuel pump,camsaft sensors.first oxygen sensor,cranksaft seal at the pulley side nad new oil cap,.i buy the car new always changed the oil with 5w30 at 6000km with filter.car drive fine it does this only in the morning for 20seconds the it is fine.no codes stored.check the long fuel trim is at 0.8.only thing i have noticed is that when this happens the ignition timing goes negative -15 and the engine act likes this then as the ignition timing advance is better.

 

Sounds like HPFP is going out. If the situation worsens over the next few weeks, definitely it's the HPFP. You mentioned you've replaced fuel pump, I"m assuming you replaced the actual fuel pump in the fuel tank.

Also, do check your fuel filter in the fuel tank, sometimes that gets real dirty and clogged, it's restrictive to your fuel delivery to cause misfire problems. Lastly, get your injectors checked out. Best if you bring it to local performance shop and have it reconditioned, optimized for spray pattern and what not.

I'm listing my opinion with the assumption that all the things you said to have replaced are all good with no problems.

 

How about some basic info? Like year, model, mileage, etc..

 

All parts that i replace is new and the injectors are brand new i replaced them a week ago!the engine is 1.6 16v 120hp non turbo 2008 year so no high pressure fuel pump and no fuel filter.130.000km.i was thinking maybe it needs an upgrade in software or sprockets gears in cams.

 

Also i notice tjat when i open the door in the morning the fuel pump is not working to prime the fuel like it used to do.when i turn the key is working