How To Fix Idle Issues R33 Gtst Rb25Det Series1 At Least The End!

[r33 gtst 300ponies]

I had idle issues like many (on stock ecu), and no real help came from this or any other forum except cleaning aac valve( one of many possible issues), or mechanic who don't wanna spend 6hrs talking you through it if they even know, so shut up listen and hopefully this helps. idle control is managed by numerous sensors all guiding the aac valve and whatever else. as such idle issues are a sign to check all your sensors controlling your ecu, its possible your burning excessive fuel to???

1) check air flow meter, first check afm, should read 1 - 1.1v at 700-900rpm (at the meter itself), higher idle higher the figure on multimeter, also shake meter a little, does it change its idle? soldered pins can break away needing to be resoldered, you may have cleaned it with carby cleaner a few thousand ago? a big no no, OK! it has a resin coating and it gets red hot for a second or two when ign turns off to burn off crap, removing this resin will make it work great for a month or so then it will read high, causing excessive fuel consumption and a shit idle also check wiring (Continuity)whilst shaking wire to ecu if your keen. why not clean it at the same time or replace?, don't over oil it, they don't need much at all.

2) check water temp sensor, if not functioning will cause extra fuel to pump in, (for cold starts), pull it out, clean any crap of it, paper towel or 400 grit plus sand paper should be more than fine, and if it has gunk on it why haven't you flushed your radiator for so long?????, then re install, it should read approx. 3.5v @ 20deg c and 1.2v @ 80deg c or resistance 2.5ohms @ 20deg, 0.3ohm @ 80deg (water from kettle and sit in it whilst cleaning), if the voltage/resistance isn't dropping from cold and when its warm it will run like shit or vice versa I guess, and definitely hammer fuel.

3) check for vacuum leaks, best easiest way is to get throttle body cleaner and spray around all vacuum lines whilst idling it will splutter and or stall if sucking in air, and all intake joins...... probably don't spray on electrical terminals it is flammable!, any leaks fix em, even a minor one will cause shitty idle, don't forget 20+ yr old hoses in a hot engine will become quite brittle and hard.

4)ok check your aac valve 3 bolts at the back of intake plenum with purple and brown electrical connections no harm in pulling it off carby cleaner, check plunger and resistances of aac solenoid (9-11ohms) and ficd solenoid (22-23ohms, to compensate for a/c), don't be brutal just ensure plunger moves freely and air can pass through to intake plenum.

5) check fuel, one change fuel filter if it hasn't for a while, unlikely cause unless its really bad but why not eliminate it, pinch the return line, does the idle return to normal pretty quickly(within a few seconds)? then your injectors need cleaning (my first issue followed by afm and needed to reset the computer)

6) check air regulator (under intake plenum) if you can be bothered, the bolts are excessible just hard to locate see remove. check resistance (70-80ohms @ 20deg), check for free movement of flap, put it in the freezer for a few minutes, did the flap move close open I can't remember, I think the manual says it backwards, put a hair dryer on it does it do the opposite? this can cause bad idle fuel issues.

7)now the throttle stop, don't touch it, if you have then keep it as closed as it realistically can whilst idling fine, any adjustment of this MUST coincide with an adjustment of the tps. these cars are made to give a rich fuel mixture just after you open the throttle so a badly set throttle stop( should be fine if hasn't been touched, EXTREMELY sensitive adjustment) and tps, if the tps reads over 0.5v you will hammer the fuel from idling, mines at 0.45v, this does obviously affect the fuel enrichment just after touching the throttle, so perhaps you want to experiment with bringing closer to 0.5v at idle/ zero throttle to give max torque from the 0km/hr, to adjust idle you should only touch the little screw on the aac valve realistically, but definitely check. a common cause of excessive fuel usage. adjusting the tps/ throttle stop should coincide with a computer reset, mine would drop 300rpm when on turbo timer until I reset the computer it seems to stop the idle control from functioning????

8) your idle should be fine now, if your keen check theres a pulsating signal to each injector or put a screwdriver on it and press your ear on the end of it you should hear a consistent click click click.... this means they should be working, possibly dirty but working.

9) check your o2 sensor!, it should bounce around 0.6v-0.9v @ 2000rpm, according to manual, mine new one bounces from 0.4-0.7v but I didn't check exact revs, your multimeter may not pick it up properly if its not sensitive enough, my old one was 0.02v-0.3v at low revs. this will cause excessive fuel usage but is less likely to cause idle issues, but just check it, they do wear out over time and if it reads a constant voltage its farked, cleaning them probably wont fix it most cases unless its very dirty, worth checking I guess, vinegar over night, I did this but it did seem to fail soon after, ive seen videos heating them with a blow torch.... but they wont last much longer than 150k give or take. new is probably best in this case. $100 autobarn direct fit, same listing series 1 and series2???? right or wrong mine seems fine now. the only real way to check them properly is with an oscilloscope, just bear that in mind and multimeters may not always be sensitive enough

after checking your sensors its wise to reset your computer, error codes.... can cause it to go into safe modes and idle/ fuel usage etc can be up to shit even after checking all this without a reset, some will do it others wont. I don't know specifically which one do don't. not to be dismissed is the CAS, make certain you accurately mark its position if removed, although any CAS issues would probably cause bad misfires etc. whilst on the dyno mine went from 260 max hp to 286hp by bringing back the timing a few degrees if that. the only way to do base timing correctly is on a dyno. download the manual for checking what it should read, simple but can't be bothered typing. I hope this helps and comes up on google search!