Weird Idle Problem

[Rolls]

So I just had my car tuned with 740cc deatchwerks injectors with stock rail and reg and z32 run by a nistune, it is an rb25det neo but with r33 intake and rb20 sensors in an r32 so it has the R33 AAC valve but only with one plug hooked up as that is all the loom has.

Now the car when I first put the injectors in untuned (was tuned for 440cc and different fuel reg) it started instantly, barely one turn of the starter and it fired up and purred like a kitten, no popping, no hunting, perfect 1200rpm idle when cold that slowly lowered to ~700rpm over 5-10 minutes however when hot it was about 600rpm and a bit shit.

During the tune we had to change the kfactor and injector latency a fair bit to get it lean enough up top (got numbers as low as 7 on boost out of a range of 255!!) and this seemed to make the idle quality suffer a bit when hot which was expected. On cold start once again it would start immediately when breathing on the key, come to 1200rpm but be poppy and a bit average but when hot great.

I then had a full dyno tune where we played with the settings further getting everything perfect, after this it would still start great, but then after 3 seconds splutter and stall, restart and after 3 seconds drop to 2-300rpm and you'd kick it, come good, and go on 3 second cycles, splutter splutter, then back to purring at 1200 rpm etc after a few minutes it would idle fine at ~800rpm but poppy and hunt from 700-900 rpm, hot idle was great.

I dealt with this for a week and then it seemingly fixed itself, back to idling at 1200, not a single rpm deviation or pop, if anything the idle was slightly too high, when hot idled perfect.

Another week later back to shit idle again.

I spoke to Pete at nistune (he did the tune) and he doesn't think there are any odd maps it could jump to to cause this, we also copied the warm map to the cold map so they are identical, It sounds like it might be a mechanical problem but the 3 second intervals just seem to random for it to be.

I tried unplugging the O2 sensor incase it was trimming too much/too little but no change, tried unplugging the TPS and no change, I also unplugged the AAC valve and no change, surely one of these should be affecting the cold idle? I know there is a thermostatic valve which is run via coolant temp, but I would have thought the PWM signal for the actual AAC would be active at all times.

What is the next thing to check? I'm guessing it might be the cold start coolant fed part of the AAC which I could try blasting out with compressed air and soaking in petrol over night, but are there any other settings in the ECU or mechanical/electrical things I should check?

Edited June 3, 2012 by Rolls

[GTSBoy]

Give the AAC a good clean out with carby cleaner as a first start, just to make sure it is clean enough to be able to move properly. Get it out of the way.

The cold start valve is powered. That's what heats it up, not coolant so much. It's attached where it soaks up heat from the inlet manifold anyway, but it's the heating element in it that does the job. You could test to see if that's all working properly.

Edited June 3, 2012 by GTSBoy

[Rolls]

There are two plugs on the AAC, one purple one on top and a orangey one pointing straight down, the bottom one is hooked up but nothing happens when I unplug it, the top one my loom doesn't have a plug for.

Does anyone have a wiring diagram or know what the top plug is for? I doubt it is my problem unless some gremlin in my engine bay gives it power randomly depending on the week, but it might be something to look into.

[GTSBoy]

The purple two pin connector is for extra air...when AC or power steering loads up the engine, it increases the idle speed. Not essential to have it connected, and unlikely to cause your problems.

[Rolls]

So the bottom connector is the PWM signal from the ECU, where does it get power for the heating element? I thought it was purely heated via coolant, esp being as there are only two plugs?

Can you confirm on your 33?

[Rolls]

The fact that unplugging the bottom plug made no difference to the idle when cold means that if the cold start heating element is indeed powered it must be powered via this plug, perhaps that is where the wiring issue is, I will meter it out and see that it is getting power.

Unless of course it is purely mechanically actuated via coolant temp, can anyone confirm this?

[GTSBoy]

No....the cold start valve is completely somewhere else. Under the plenum.

The AAC is idle control. Brown plug.

The FICD is Fast Idle Control Device. Purple plug. Not heated - it's a solenoid.

The cold start valve is the one under the plenum. Biggish thing, two fat hoses, one on either side. One electrical connection (two wire).

[DVS JEZ]

No....the cold start valve is completely somewhere else. Under the plenum.

The AAC is idle control. Brown plug.

The FICD is Fast Idle Control Device. Purple plug. Not heated - it's a solenoid.

The cold start valve is the one under the plenum. Biggish thing, two fat hoses, one on either side. One electrical connection (two wire).

The neo has the cold start coolant fed part on the aac/iac valve.

EDIT: misread. Didnt realise it had r33 intake

[Rolls]

No....the cold start valve is completely somewhere else. Under the plenum.

The AAC is idle control. Brown plug.

The FICD is Fast Idle Control Device. Purple plug. Not heated - it's a solenoid.

The cold start valve is the one under the plenum. Biggish thing, two fat hoses, one on either side. One electrical connection (two wire).

Where abouts under the plenum, near the injectors/under the TB ?

[Rolls]

Ok found the air regulator, can't seem to find any plugs on it though, I'm guessing that is probably what is loose though.

[Rolls]

Hmm after wiggling every thing around it seems better, not 100% fixed like it was though, not sure could be a coincidence, are you 100% there is a wire there?

The block is neo and the intake/aac is r33, so I would have used all the r33 stuff and Im pretty sure the air regulator was attached to the intake manifold so that would be r33 as well, can't see any pictures of an electrical plug in the r33 manual either.

[GTSBoy]

It's electric in the R32s......I've seen an R33 one and it looked essentially the same, so I was just assuming it was electric too. If it's not electric, then it really needs to have coolant lines on it, otherwise it ain't gunna get hot enough fast enough.

Just google looked. These things....http://www.google.com.au/search?tbm=isch&hl=en&source=hp&biw=1337&bih=549&q=r33+air+regulator&gbv=2&oq=r33+air+regulator&aq=f&aqi=&aql=&gs_l=img.3...1206.7754.0.8132.17.10.0.7.0.1.321.1619.4j1j4j1.10.0...0.0.xIsTD6DUtIs

(look at the third and 5th hits)

have an electrical connector on the other side.

Edited June 4, 2012 by GTSBoy

[Rolls]

See mine looks identical to that but I've felt all around it and can't feel where any plug would go on, there are no spare loom connectors down there either, nor is there one in the manual.

Maybe I need to get under the car to see it, can anyone confirm it definitely does have a plug?

[Rolls]

ok found a spare blue plug coming out the injector loom, this could be what it is for, I cant for the life of me find a plug on the cold start valve though.

[Rolls]

Ok it does have a plug it is just in a prick of a position, I put it on, guess we will see what happens tomorrow, I have absolutely no idea why it idled perfectly for about a week though??

[GTSBoy]

The weather has been through some sizable temperature swings lately. Frigidly cold in the middle of May, warmer late May....back to pretty cold just lately. Could be as simple as that. Couple it with changes you've made to the tune across that time, and anybody's guess is as good as mine!

[Rolls]

Well it went from bad to good to bad after the final tune, and was also good before the first tune, so it is possibly temperature related but I am quite confident the two periods where it idled well were hot and cold, definitely a possible scenario though.

I'm thinking this is two seperate issues, a vac leak causing the popping on idle etc, and then the cold start valve obviously not being plugged in, tomorrows cold start test will be interesting anyway.

Thanks for the help so far.

[Rolls]

Ok made absolutely no difference with it plugged in or not, I tried unplugging the TPS, AAC, O2 sensor and none of them effected the idle at all.

I held the revs at 1500 and it started to hunt between 900 then back up to 1500 then back down and pop and fart, got a lot better after a few minutes and when warm it went away, this says to me it isn't an idle problem, I can even feel it missing when cruising at 60 in 5th then come good then miss again, goes away when warm.

I am starting to think I have a misfire or an injector not firing properly when cold, unsure how to diagnose this further though?

I will put the consult cable back in and check the timing isn't shifting due to say a stuffed CAS or something as well.

edit: Brand new plugs as of 500km ago 0.8mm gap with 6 heat range.

Edited June 5, 2012 by Rolls

[GTSBoy]

Any power on that air reg's connector at all? Won't help if it's not powered.

Just making sure that train of thought it exhausted before moving on.

[Rolls]

Yeah I'll multi meter it all up.

I just get the feeling it is something else as it did idle perfectly for a week twice, this hasn't been connected ever.