Weird Idle Problem

[GTSBoy]

TPS should be about 0.45v at idle. 0.88 is considered "open", not "closed"

[Rolls]

We adjusted the trigger voltage to 1.0v I believe, you can confirm by the "closed throttle" being at 1 and when I touch the throttle and it goes above 1v it goes to 0

When we adjusted the trigger voltage below this it would just rev and hunt weirdly, I am positive it is in the idle mode when the throttle is closed as it isn't doing this.

Edited June 13, 2012 by Rolls

[DVS JEZ]

Ok thats fine as long as its in the idle mode.u must be running an rb20 ecu if u can adjust the tps trigger voltage via ecu.

There may be something else causing it to go out of idle mode to make it run 30degree's timing. But try adjusting the tps anyway. Theres 2 small screws u need to loosen slightly then rotate the tps. Have the key on and use the consult. Adjust the tps to .7 if its at .8 now.

Have a play around and monitor if the idle stays stable

[Rolls]

Ok today the idle was great again, started first go, no pops then after about 10 seconds would get an ever so slightly mild pop, idled great the entire way to work.

log says ~1100rpm+-20rpm so stable, water temp was about 20c, tps 0.88, 30 degrees timing, 2.08-2.11ms injector, O2 still reading lean. After about a minute idle dropped to ~900 and timing dropped down 1 degree at a time to 26 degrees eventually to 15 degrees when warm.

The only difference between today and yesterday is it is much colder this morning and I left the car outside, the other thing is I drove straight home without really getting over 60 last night. It is possible the plugs are just fouling up on boost maybe?

Can try playing with the TPS but I think it is something else, it just doesn't make a whole lot of sense to go from almost undriveable to perfect over night and then back again.

Edited June 14, 2012 by Rolls

[DVS JEZ]

Its definately a weird issue as its intermittant. Best bet would be get a wideband on it. Check it at idle. My guess is its leaning out causing a lean pop.

Ive had similar issue's with a z32 rb25 NIStune. Idle afr would be stable then every minute or so would lean out and start popping. I left the 02 sensor off(which i normally do anyway) but turned on the 02 flags around idle which stabilised the afr's. I spoke to Matt about this and he was goong to check it out for me

[Rolls]

I have had weird idle issues before with my idle going as lean as 17-18:1 when hot, but then dropping back down to 14:1 randomly.

The fact that the O2 sensor says it is lean at cold start idle vs rich when warm could be evidence of that, wish I knew someone with a wideband as it is a pain in the ass to drop it somewhere just to check the cold idle.

How reliable is the rich/lean condition of the O2 sensor, should it be lean at idle? You'd think when cold it would want a rich idle to be stable.

Edited June 14, 2012 by Rolls

[GTSBoy]

O2 sensors can get too cold at idle to respond well, and can sit on the lean side. The ECU might add a bit too much juice to compensate, giving you a path to fouled plugs.

[Rolls]

I don't think the O2 feedback works when cold, I've unplugged the O2 sensor and there is no change to idle until warm.

The O2 does seem to work though, if you give it a rev it flicks over to rich.

Edited June 14, 2012 by Rolls

[Rolls]

Got it fixed, was a coupled of problems, a) the AAC was seized and not responding, put a new one on and it made the idle more stable, but still was stumbling and doing weird shit. Eventually got it nice by just playing with the injector latency settings and then tweaking the mixtures down low, took them forever as it was very fiddly and just didn't want to idle nicely but now its pretty good, still pops occasionally but it is stable at ~750, doesn't hunt and comes back to idle nicely if you are on boost then immediately clutch in.

I am not confident the problem has been fixed though, I just think it has been masked, as occasionally when driving it will stop the occasional pop and get even smoother and never pop, still I don't really care anymore as long as I can do skids and chirp 2nd.

[DJ-Static]

Possible AFM issue? Do you have the NisTune software? Most sensors/acc etc. can be monitored on the consult panel. You'd think a cold log would detect a sensor issue. Particularly if it comes good once warm.

[Jayden.K]

do you think its the same issue im having a seized valve (maybe from sitting around for so long)

http://www.skylinesaustralia.com/forums/topic/423722-another-idle-hunt-issue/

please read my post

[Ben C34]

Possible AFM issue? Do you have the NisTune software? Most sensors/acc etc. can be monitored on the consult panel. You'd think a cold log would detect a sensor issue. Particularly if it comes good once warm.

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