Gts-4 Problems

[OMGGTR]

Hi guys, finally got my 2nd skyline used to have a 34 non-turbo and now got something with a little more room to play with, picked up a sweet 92 gts-4 for 7 grand knowing it needed some money spent on it to get it right... now the question is!

Cold start I've noticed light struggle but u dont need to accelerate to make it not stall, it will slowly pick up revs and sit around 8-900 roughly now its running rich as dark chocolate and i believe an O2sensor will fix it but that's just me guessing the reason I'm asking is the O2 sensor will most likely fix the richness but i don't think it will fix my next problem which is.... after 1 min roughly of idle it will start rev dropping to 300 revs then back up to 1000 then back down and that don't stop, what could it be?

now i could go prostituting it around to every guy that can say yeh its this or yeh its that, but i thought i give you guys the verdict first since i usually find the right answers here from guys that know what they are actually on about lol

any reply will be taken into consideration thanks a bunch !

[paulr33]

check the basics

check timing with timing light

reset stock ecu

change 02 sensor

[vinnie32GTS4]

check the afm too