Mike B Posted December 9, 2007 Share Posted December 9, 2007 Hi Guys. Reading through the forum trying to find a definative guide to the Idle system for the 2jz, and I'm not coming up with any definative info. Like many on the forum my car is starting to idle oddly from time to time (mostly when I don't use it so much) but it's a problem I want to fix, and I can't find much relative info. It's a problem I have heard from a lot of different members now the cars are getting older. Would it possible for one of our fully clued members to write a brief guide to the idle system, related ecu component, it's function (stages through cold start to warm idle), and the sensors it draws info from / controllers it sends commands to....? It would be really handy to have a bible / sticky for this info so we can track down all the possible causes and check components to figure out what's going on - there seem to be more idle problems than ever. It's a niggly problem that garages charge a lot to diagnose, and those of us without stock ecu's can't plug diagnostics into. This is my (limited) understanding so far; Idle system is on a closed loop (needs explaining as I don't know what a 2jz closed loop is) and when revs rise it hands over control of the engine to a main ecu load map (for want of a better word) Cold start; stock ecu just puts in a set mix of fuel at a set rpm as the o2 sensors don't work until they are hot. When the engine is hot enough (temperature sensor) it then switches to the O2 sensor for warm idle on a targer afr/rpm. I'm also unsure what, where and function of the idle control valve... I'm sure our top tech bods, and certainly Ryan could do us proud...? Quote Link to comment Share on other sites More sharing options...
dandan Posted December 9, 2007 Share Posted December 9, 2007 I can write something tomorrow if I get 10mins spare..... What exactly are your car's symptoms and what are any sensors/logs telling you when you are in problem territory Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted December 9, 2007 Share Posted December 9, 2007 Hi Guys. Reading through the forum trying to find a definative guide to the Idle system for the 2jz, and I'm not coming up with any definative info. Like many on the forum my car is starting to idle oddly from time to time (mostly when I don't use it so much) but it's a problem I want to fix, and I can't find much relative info. It's a problem I have heard from a lot of different members now the cars are getting older. Would it possible for one of our fully clued members to write a brief guide to the idle system, related ecu component, it's function (stages through cold start to warm idle), and the sensors it draws info from / controllers it sends commands to....? It would be really handy to have a bible / sticky for this info so we can track down all the possible causes and check components to figure out what's going on - there seem to be more idle problems than ever. It's a niggly problem that garages charge a lot to diagnose, and those of us without stock ecu's can't plug diagnostics into. This is my (limited) understanding so far; I like you don't have full picture, but i do have a few comments which may help! Idle system is on a closed loop (needs explaining as I don't know what a 2jz closed loop is) and when revs rise it hands over control of the engine to a main ecu load map (for want of a better word) idle control, closed loop, doesn't really come into it as such, throttle position/closed throttle sensor governs when idle control takes over, but as for the parameters that control the idle control valve, i am also at a loss! Cold start; stock ecu just puts in a set mix of fuel at a set rpm as the o2 sensors don't work until they are hot. Yes cold start is a set duty cycle depending on water temperature, but i also suspect that there is another factor, which is why i think i have a problem as my idle speed does not increase by much on cold start? When the engine is hot enough (temperature sensor) it then switches to the O2 sensor for warm idle on a targer afr/rpm. Thats the way i understand it, apart from what i have mentioned above. I'm also unsure what, where and function of the idle control valve... Its on the back of the plenum, and it controls the amount of air that is bypassed into the engine on idle. I'm sure our top tech bods, and certainly Ryan could do us proud...? i am also very interested to find out just what else has an effect on the idle control valve. Quote Link to comment Share on other sites More sharing options...
Ryan.G Posted December 10, 2007 Share Posted December 10, 2007 Start off by reading this http://www.autoshop101.com/forms/h26.pdf Then any questions fire them on here 2jzgte uses a stepper motor Ryan Quote Link to comment Share on other sites More sharing options...
b_have Posted December 10, 2007 Share Posted December 10, 2007 I didn't think the VVTIs had IACVs but Ive never owned one so probably wrong. Quote Link to comment Share on other sites More sharing options...
Ian C Posted December 10, 2007 Share Posted December 10, 2007 The VVTi uses it's fly by wire throttle control to perform idle control. Quote Link to comment Share on other sites More sharing options...
Ian C Posted December 10, 2007 Share Posted December 10, 2007 On non-VVTi engines, the idle control is performed by a stepper motor at the back of the intake plenum. It's located top left of this picture: http://www.mkivsupra.net/vbb/attachment.php?attachmentid=13939&d=1112558977 There is a stepper motor controlled by the ECU that moves a plunger in and out of a hole into the plenum to control the amount of air going in. There is also a one way flap valve past this which stops boost pressure leaking back out again when off idle. If you want to know what sensors affect what then the attached table is invaluable -Ian Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted December 10, 2007 Share Posted December 10, 2007 Start off by reading this http://www.autoshop101.com/forms/h26.pdf Then any questions fire them on here 2jzgte uses a stepper motor Ryan Thanks Ryan, very helpful:) my ICV has been giving me trouble ever since i got the car, my initial resistance tests on motor connectors where all ok, same went for the ECU water temp sensor, but there is obviously something wrong as cold start is only about 100-200 RPM higher than hot, it will also change when electrical load is applied, lights, air con etc, and after a brief read of that if the Supra uses it for deceleration which i think it does, as i have always seen very rich AFRs on closed throttle, so IMO the ECU is chucking the normal duty cycle to the injectors on closed throttle, but the IAC is not opening, which would even out the AFRs, Now for some more testing. Quote Link to comment Share on other sites More sharing options...
Mike B Posted December 10, 2007 Author Share Posted December 10, 2007 The VVTi uses it's fly by wire throttle control to perform idle control. I will have a good read tonight, but I know for a fact that my engine uses the stock ecu for the throttle, and therefore idle system too, the V-pro only runs the engine, not the throttle. So it should be possible for me to check everything according to the manual. Thanks for the help so far Quote Link to comment Share on other sites More sharing options...
Ian C Posted December 10, 2007 Share Posted December 10, 2007 Does your idle fluctuate and do you get pops and bangs on overrun? (that's at Tricky btw ) -Ian Quote Link to comment Share on other sites More sharing options...
dandan Posted December 10, 2007 Share Posted December 10, 2007 I didn't think the VVTIs had IACVs but Ive never owned one so probably wrong. The only ones that will have will be the ones with standalone ecu's where the mapper cannot setup the DBW 100%. In those cases the addition of a ford type bypass valve is not uncommon. Or the other option is to live with the (not as uncommon as I thought amongst our standalone vvti enthusiasts) "I have to blip the throttle a bit and coax her into life on the cold cold mornings" method of cold start....crap if you ask me. Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted December 10, 2007 Share Posted December 10, 2007 Does your idle fluctuate and do you get pops and bangs on overrun? (that's at Tricky btw ) -Ian Very occasional pops from exhaust, which i would expect due to the rich AFRs on closed throttle, but other than that idle is stable, but i suspect that if its had the problem before i got it, its been compensated for by throttle valve adjustment, which i have maintained when re adjusting etc. Quote Link to comment Share on other sites More sharing options...
Ian C Posted December 10, 2007 Share Posted December 10, 2007 I had some of those symptoms once when the TPS was adjusted all wrong and the "closed" switch in it was never getting set so it never cut fuel on coast down and idled oddly (I guess as it thought I was driving and yet constantly about to stall it). Might be worth a shufty? The overrun did sound cool though I just crack the throttle open half a percent to emulate it when I'm feeling all chav-like -Ian Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted December 10, 2007 Share Posted December 10, 2007 Unfortunately so to speak, my TPS is set fine, it will go to no fuel but between the throttle being shut and AFR showing it, i get AFRs of anything from 12 to 10, which is what leads me to believe that the ICV is not functioning as it should:( Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted December 11, 2007 Share Posted December 11, 2007 I noticed on that Toyota document that there is no mention of the 2JZ engine, although it uses the stepper motor type. Quote Link to comment Share on other sites More sharing options...
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