Hi everyone, trying to figure out what's wrong with my car. (250GT VQ25DD)
Only have a Injen cold air intake, although it was meant for a G35 and so I have 1 small hose, i think it's for vacuum that's disconnected.
It started with a very slight, barely felt, misfire during idle.
Now it's built up to be quite bad, spewing black smoke while driving, with bad fumes on idle.
Consumption's shot to hell, if I idle too long it'll go into limp mode, and sometimes it's hard to start.
I've changed the spark plugs, then I changed my coils - to wrecker items - and nothing's changed.
My plugs are cooler than recommended though; NGK LFR7s instead of the 5s, but the problem existed before I changed my plugs.
I can try running hot plugs again, but I think the problem lies elsewhere.
ECU reported initially that Bank 2 was running rich. I got my hands on a OBD2 scantool and reset everything, including ECU learning.
There was no change, then both Bank 2 and Bank 1 were reported rich.
I've heard on the Golf's when the high-pressure pump goes faulty it continuously dumps fuel at a high rate, even at low rpm.
I guess I'll try cleaning the injectors next; although do you clean direct injection (high press)injectors the same way you clean tb/port injectors?
Also, the initial problem was more apparent after I decatted; although my car only has upstream O2 sensors.