R33 Idle Issues

[barretdenis]

Hi

My R33 has developed an odd idle issue when you back off acceleration.

The car has an auto box. You can be driving along and take your food off the gas to slow down for a set of lights and the Revs will occasionally drop as low as 500rpm and then bounce back to normal; this does not happen every time though.

I have had two occasions when the engine stopped, however it starts and idles perfectly and drives without issue.

I've cleaned the AFM, new air cleaner, new plugs. Any advices?

Thanks

Denis

[GTSBoy]

Search for one of the gazillion posts on the subject, using terms like IAC, AAC, IACV, idle, stall.

[barretdenis]

Advice like that is commonly referred to as political speak - an answer when you have no bloody idea; so why bother replying

[GTSBoy]

Ha. Funny. You are so wrong.

[dyl33]

Could be aac valve needs a clean, diy thread http://www.sau.com.au/forums/topic/110431-diy-aac-valve-cleaning-idle-reset/

[89CAL]

Atmo BOV? - Get rid of it

Factory ECU? - After cleaning AAC valve, try resetting the ECU (disconnect battery, operate lights etc, to drain residual power, re-connect battery, start car)

It has been covered qutie a few times before.

[barretdenis]

The engine was fully rebuilt with forged piston, greddy intake manifold, larger injectors, hi flowed turbo, turbosmart blowoff valve, bigger intercooler, Z32 AFM (cleaned regularly) etc etc. The engine has only done 12,000kms in 4 years. There are no mud issues in the AAC or any of the usual issues that are eluded to the great how sections.

Idle is perfect with no fluctuations while sitting. It's only occasionally when you take you foot off the gas to slow for lights etc that the idle drops to 500rpm or lower and then rights itself. This has only occurred in the last few weeks.

I was swaying towards the Turbosmart blowoff valve, but all checked and cleaned and appears OK

Would a TPS cause this? I thought it unlikely.

Sorry if I was somewhat grumpy; you get that way when you're over 60.

[GTSBoy]

turbosmart blowoff valve, .....

Turbosmart blowoff valve,

See Cal's post. Then shitcan the BOV if it is venting.

[89CAL]

I dont have any experience with Autos but I had issues when I went from atmo BOV back to stock. Cleaned AAC and all that and it didnt help. Reset the ECU and it returned to idle fine

But im not sure if you are running stock ECU

The TPS on auto has a digital and analog input to the ECU. The on off part is important on Autos if I recall correctly ( the analog voltage signal is important to both auto and manual) the digital input is easy to check with a meter, run a continuity check accross the 2 pin plug with throttle closed and then open the throttle. It should go from closed circuit to open (or vice versa, been a while since I checked)

The other analog sensor is best checked with consult or the correct software for your ECU. Should be 0.45V

[barretdenis]

Thanks Cal. I'm running a Nistune ECU as it was the best with the Auto. I will check the TPS.

[Badgaz]

tighten the bov spring if it has adjustment.

[skylinecouple]

Hey Dennis, try turning your idle air screw counter clockwise till the engine starts to rev higher. Then turn it clockwise one full turn. Sometimes people fool around with this screw and it can cause major idle issues as you have described. Another possible fix could be to lean off the fuel under 800rpm but this depends on the tune in that area so may not help. I am always concerned about changes to the blow off valve as this usually always causes issues. Make sure it is plumbed back.

[89CAL]

RB25's tend to want to run a bit rich at idle. I think as rich as 13.2:1 I've seen to give a nice smooth idle.

Off the top of my head I used to run 13.6:1 when I had the Power FC in mine.

Agree about the idle screw, was thinking that the other day. If its wound all the way in the solenoid/valve might be able to compensate just enough to idle, but when its going from higher revs to idle, it can't adjust quick enough or far enough to give a smooth idle.

[barretdenis]

Well after checking all possibilities I turned to the Turbosmart BOV. After winding it back to the softest setting I discovered no more idle issues.

Why?? You tell me.

[Scott Black]

Well after checking all possibilities I turned to the Turbosmart BOV. After winding it back to the softest setting I discovered no more idle issues.

Why?? You tell me.

Easy the stock.ecu likes having the stock bov, a aftermarket bov on softer settings are more like the factory bov

[GTSBoy]

So long as it is recirculating.

[Ben C34]

Softest?