Basically idles like a dream but if I give it a rev it will stall on rev down, I have checked MAF all OK, Checked IACV / AAC and works fine, I even checked it back to Pin 4 at the ecu, went one step further I pulled the injectors back out had them checked and all ok. double check every hose replaced the spring hose clamps with normal hose clamps, still stalls! So I put the multimeter on to pin 4 to measure voltage to the AAC and all I get is a constant 0.76V no change when the motor is running or when it stalls. O and when I set idle with the AAC disconnected at 650rpm turn motor off reconnect AAC start car and idles at 650rpm no change connected or disconnect. So the question is Could it be the ECU or what tells the ECU to add voltage to the AAC, and yes I have checked the TPS it is set to 0.45V PLEASSSE HELP, I also checked continuity from ECU pin 4 to AAC plug and the other pin has earth, also replaced the hole IACV unit with my spare no success.
Not a good idea to change the spring hose clamps to the 'normal' variety. What are the O2 sensors telling you?
Doesn't hesitate Doesn't hesitate when you rev it which I thought was a normal sign for vacuum leak, also I drove it to work and it was stalling and that night it was fine, then next day back to stalling again, and I have checked every connection also had plenum off 3 times
02 using ECU Talk instead of Nistune OK at 2500rpm the left one dropped to almost zero and then started going up but the right one stayed around 0.1 but now varies between .05 and .3 and now with nistune sitting around .42 then fluctuates when you raise the rpm
Timming OK previously ECU timing at idle was 25deg but once you raise the arp slightly went to 15-16 deg climming as the rpm raised, now ECU at idle reads 15deg I rechecked with Timing light nd was sitting at 25deg, so readjusted to match ecu. Yes this is an auto to manual conversion but I am running a manual tune with Nistune?
Wiring to ecu Checked Wiring back to ECU and it's OK as previously mentioned, also replaced Idle valve.
More testing OK so I decided to run some more test, Firstly grabbed the spare IACV unit, and plugged it in also plugged multimeter in to measure volts, so at idle was reading the same as at pin 4 at the ECU 0.9V as I gave it a good rev and at rev down volts spiked quickly to 10v then went straight back to .9V but the solenoid didn't move, using digital multimeter. Next I took the Unit to the work bench and applied 1.5v no action then 3V no action but at 4,5V the solenoid started to operated at 6v opened even more at 12v it comes in solid. So I disconnected the small hose connected to the boost sensor to introduce a small vac leak, and low and behold I can give it heaps of revs and it won't stall on rev down. anyway can some one unplug their AAC and measure Volts as I am still thinking that the ECU is not delivering the volts needed to slightly open the AAC Solenoid? also when I check the AAC% on ECU Talk it will go from 10% to 80% depending on revs.
I TAKE IT it was a auto tran car and you have fitted a manual gear box . Are you still using the same ECU you were using on your auto box , NISTune mother board ROM alters the tune but does not alter the loom from the old auto gearbox. Autos idle @ 15deg advance, when placed into drive the car timeing advances to 25deg to stop the car from stalling with out throttle. The plug that use to be connected to the switch on the gearbox to signal the advance timeing to advance to 25deg maybe your problem , Try grounding this not used plug wire to earth. then reset the timeing to 15deg again. Manuals gearbox don't have this switch to alter timeing only a reversing switch. Auto ECU will show idle at 25deg advance with this switch wire disconnected !
Pretty rare for the ECU to be involved but it can pay to check both the earth strap and the ECU connector if your worried about the signal It is possible it could be an air leak as stated but generally you are right in that the idle will be affected (generally) if their is an air leak. I am assuming you have already done the blow pass test and fuel pressure tests as per the manual just to eliminate them completely, so indeed it does sound like either the IACV / AAC is a problem but based on what you have stated it does not sound electrical but that it is either clogged with carbon or the plunger is sticking as this would be symptomatic of the problem you describe (IACV /AAC mechanical problem rather than electrical) There should be a difference between cold start and warm operation if the IACV/ ACC is the cause (you have not indicated either)- just remember the electrical test will not tell you whether the plunger is working correctly or whether there is excess carbon in the passages - you can only tell this with a removal, inspection and service if needed(unfortunately) It is not a common problem but with the Z's now having 20 yrs+ of carbon and wear over time but a few here have had an issue as you described before where indeed it turned out to be plunger or carbon involved in the IACV / AAC Refer to EC 92 Engine and Control section) in the manual for a full guide on working through the problem Hope that turns out to be helpful - goodluck JC
Yes it is a Man to Auto and I am not using the Auto ECU I am running a Different ECU with Nistune for over the last 12months with out issue, I will how ever find this plug and check it, I followed an extensive how too when I did the change over and maybe I have already done this.
