Idle hunting R33 GTST w/ RB30

[brother_david]

Hi, i've got a real annoying idling problem!

Built an RB31/26DETT w/ R33 GTST harness and AAC valve (Auxiliary Air Control Valve/Idle control). At idle the car is revving between ~1000-2500 rpm and i havent got an idea of what might be giving me these problems.

I have no problems revving it and the rev is stable as long as i hold the foot down to keep it above idle.

Had no problems with the AAC on the last engine. When i disconnect it now there is no change what so ever.

Using a Q45 throttle house and TPS, dont know if this could be the problem, i've set the voltage to 0.45 according to my SAFC-II.
Not sure i've reset the TPS correctly though, have tried disconnecting the TPS for 10sec but this might be wrong?

Also using dual Q45 AFMs, dont know if one might be damaged but it seems fine above idle.

Hoping you can help me with this

/Dave

[Matt]

With the idle problem, are you seeing the TPS idle light work at all?

With the TPS, make sure the TPS light inside the Consult display page turns off just when you push the throttle

There should be a smooth transition from idle maps to main maps

You say there is no difference when AAC is disconnected which means that is potentially the source of troubles. Does the AAC work (ie is it pulsing if you have it connected)

Where you mention the SAFC-II you have the TPS plugged into this? How is that fitted into the Nistune side of things (used for the Q45 AFMs I assume and then into Z32 ECU?)

Realistically you may need to backtrack a bit

If you can run Z32 ECU mapped for RB25 with single Q45 AFM and TPS without the SAFC firstly and get that stablised and then go for the SAFC and dual Q45 once you get that working

[brother_david]

Thanks for your support!

The TPS light is on, and comes off just as i push the throttle.

About the AAC, Im going to take it apart today and clean it, im using a plate with a pipe fitting since its the old RB25 AAC and im using the GTR head w/ intake. It did lay around a fair bit of time in the garage before i fitted it, might have gooe'd up.

Yes, the TPS is connected through the SAFC but that makes me think i maybe should skip having that function, one less potential problem.

Im going to look further into the AFMs/MAFs cause searching on similar problems at SAU often came up beeing the AFM. Weird though since itll let me rev it.

Im also going to take a closer look at the cold start valve and also check once again for potential vacuum leaks, didnt find any last time. This is really making me rip my hair off

[Matt]

Yeah thats why I'm erring on the side of going back a few steps to find out what does work (its going to be a pain doing this) but at least you might figure out what is causing it. Because of the mutliple changes its hard to know where to start.

The AAC is the best guess becaue if that isnt working then you know what to blame (either that or the SAFC)

[Matt]

I was out and checked the cold start solenoid, a hose was loose. Tightened this and it made the idle much more steady, when cold it was more or less crisp.

Got the old problem still though but only when warm now, and also less intense, revving between 800-1400rpms. Going to check for further leaks and also pull the AAC apart to check it out.

On top of this i havent got the slightest idea of what timing to start out with, feels like to old timing from the RB25 is set a bit to high for this engine, with figures above 45 in the mid revs but thats a later problem.

[brother_david]

Have been out getting my hands dirty again!

Took the AAC/Idle control apart and cleaned it, put it together and it seems to have done the trick! Not sure though since i havent taken it for longer drives yet, also want to get it real warm before i can say that its definietly gone.

Not sure that i've reset the TPS according to procedure. Before i cleaned out the AAC the car would have a steady but high idle, around 2000rpm but as i said, it was steady.

Now as far as i know the idle should stay the same when i pull the TPS cable, but it didnt, does anyone know how to reset the Q45 TPS on a Z32/RB25 ECU? The SAFC-II says 0.45v but Nistune reads 0.38v TPS.

Been driving the car with the TPS connector out and it revs alot better, dont think this has with the SAFC-II to do since its a read only function but i might aswell just disconnect the TPS cable going to it anyway.

[Matt]

Normally set the position so it transitions smoothly from idle to off-idle (generally when TPS idle light goes off after throttle pressed slightly)

[brother_david]

Problem with idling between 1000 & 1500rpm is still there!

Been up and down around the engine looking for vaccum leaks with starter gas but havent found any more.

Heres one clue though; when i disconnect the TPS the idle stays at 2000rpms, doesnt go up or down. Does seem like it has something to do with the TPS doesnt it.. Need help with this

To get the TPS volts correct on the Q45 i rotate the TPS sitting on the throttlebody but theres still the problem with getting the ECU to understand the correct volts, havent tried rotating it when the engine is on yet though, doesnt feel like i should make the right difference.

Matt, you wouldnt happen to be able to give me some figures Nistune should have with the 1600cc injectors and a single Q45 AFM on the RB25 harness Z32 box? As for now i seem to need to run it richer then a k-constant of 146 i've calculated earlier.

[Matt]

email me a bin and log file and I see if I can repeat here

Log file must have rpm, maf, tps, flags1, inj time at a minimum. Do the log in stream mode with at least those set and send that and a BIN file to me to try on the bench

I want to see your inj time holding 2000rpm and see if I can repeat here. Also look at your TPS voltage going from idle to off-idle

[brother_david]

Thanks for your support Matt!

Actually I've had some progress, thats why i havent written anything in acouple if days.
The hunting is gone, though the idle still is rough but its 1600cc inj so ill probably have to work a miracle to get it real good.
For now im running one turbo w/ AFM and the other turbo witout its AFM connected, actually works, not sure if that was a problem though so im going to connect it and see some potential difference.
Also the SAFC doesnt seem to jerk around with the TPS, since it borrows the signal volts by just beeing soldered around the ecu wire.
I have a problem with cyl 1's coilpack, doesnt seem to give any spark on idle, going to switch it around to get some real results and see if its the coil or sparkplug beeing the problem.

Now to the fun part, been pushing it alittle bit, still getting 10.0's in A/F under load but it lets the wheels spin easily in 3rd, havent had the b*lls yet to try it in 4th. Its really basic mapping on both fuel and timing so far so theres alot to get still.

[Matt]

Sounds like you're getting there. The single MAF may be sufficient for now?

Guess work on the coil problem first (causing your rough idle?). Once that is fixed then bump up the latency a little if idle is still a problem