Hi there, i created an account in the hopes i could get some advice on this ongoing situation i am having with my 3800 series 2 l67. The idle is extreme and wants to just take right off in any situation. A cold start will produce 2k RPM until the coolant temp is around 135-155 (Stock thermostat is 192 I believe? so its still closed) then jumps to 3k RPM and stays there. Putting it in Drive will lower it to about 1700 RPM but it seems as though that is solely because of the transmission engagement as the engine still wants to take off. I can get to 40MPH without touching my throttle, maybe even more! I'll list below everything i have done chasing this issue and any feedback will be appreciated! I cant call myself a professional mechanic but i enjoy doing my own work, and bought this car after it sat for about three years after the water pump went bad on my sister.
Things i have done with no effect:
-Replaced IAC Valve
-Replaced TPS sensor
-Cleaned throttle body and replaced gasket
-Replaced coolant temp sensor and T-stat
-Replaced upstream O2 sensor(at one point i had a Closed loop fault from this sensor)
-Replaced Fuel pressure regulator
-Checked rubber pieces on hard vacuum lines, replaced both T's
-Checked soft vacuum hoses, no noticeable cracks
I seem to be getting accurate data from my MAF and MAP sensors from my handheld computer, so i haven't looked into them too much. The MAF was replaced shortly before the water pump went out, while not "new" it isn't worn.
Other work i would imagine would not contribute to this issue but was recently done
-Water pump and Coolant elbows replaced (dumb trash plastic ones)
-Belts replaced
-all fluids refreshed (coolant, oil, S/C oil)
-K/N Air filter cleaned
I was thinking maybe the O-rings around the injectors have gone bad and are letting air into the the cylinders? At this point it is mostly guessing for me, I have read that a vacuum leak would cause a high positive fuel trim (makes sense) but my LTFT is -11?
Any and all thoughts are welcome!!
