Ian C Posted February 7, 2004 Share Posted February 7, 2004 This morning, my Supra decided that it would stall, or at least try to stall, the engine every time I lifted off. Symptoms are: Lifting off the throttle causes the revs to drop below the idle point - engine has a fit and pinks a bit, ECU tries it's best to recover the situation. The higher the revs when I lift off the more chance it will die despite the ECU's best endeavours. If I crack the throttle open a miniscule amount, so that the throttle cam doesn't even seem to move, it has a struggle. I've tried: Checking the hoses. Lots of them, several times. Bypassing the stock BOV Swapping the BOV out for another one Cleaning the Idle Control Valve Oiling the springy thing under the throttle position sensor that cushions the butterfly when it tries to slam shut Unplugged the VSV on the pressure tank as it makes lots of clicky noises when you open the throttle Reset the ECU That's the search of the BBS exhausted. I'm off out now as the car still drives fine in any situation other than anything but the gentlest lift-off. Discuss please I'm hoping that I've cured the problem and the ECU is still relearning the car. Laughable I know but I'm an eternal optimist. -Ian PS the first time I noticed a problem the sequential system also seemed to tie itself in a knot and overboosted the first turbo. It's been fine since, dunno if it's related or a red herring. Quote Link to comment Share on other sites More sharing options...
Supragal Posted February 7, 2004 Share Posted February 7, 2004 Uh oh, aren't you the one that normally answers this type of question? Quote Link to comment Share on other sites More sharing options...
veilsideTT Posted February 7, 2004 Share Posted February 7, 2004 My auto does this due to my Hks BOV. If I just tweak the throttle a bit to move forward and then brake to a standstill, the revs drop below the idle point and sometimes she will stall (very rarely!). This is due to my BOV dumping the little bit of boost i made whilst quickly moving, the ecu miss calculates the amount of air in the system as it doesn’t realise I dumped to atmosphere as apposed to re-circulating the air back into the system. Thus causing a bit of a drop in the revs and sometimes feeling like shes going to stall. Though you don’t have an aftermarket bov! You could have a leak somewhere in the recirculation side of things which may cause your car to act the same way as mine does. Hope this might help a bit. Scott By the way, this "aftermarket BOV stalling thing" is only supposed to happen on AUTO's. Quote Link to comment Share on other sites More sharing options...
Terminator Posted February 7, 2004 Share Posted February 7, 2004 Have you had the coils out recently? O2 sensor? Quote Link to comment Share on other sites More sharing options...
Ian C Posted February 8, 2004 Author Share Posted February 8, 2004 Right - additional info. Turning on my lights still raises the idle correctly, which is handy as this means the car is less likely to stall However, thinking back to it, since I got the car serviced I've driven everywhere with my lights on except for saturday morning as it's been dark so this problem may have manifested itself because of something done during the service - any clues? I just had a service and got some NGK plugs installed so yes I've had the coils removed very recently. I can't make the connection between liftoff to idle problems and spark plugs/coils yet, can anyone explain to me how some problem with sparks/coils could cause these symptoms without any other nasties at all? (Driven about 400 miles this weekend with no problems barring the liftoff-> idle stuff) Does anyone know the correct voltage output of the O2 sensor so I can check the diagnostics port with a multimeter tomorrow? -Ian Quote Link to comment Share on other sites More sharing options...
dude Posted February 8, 2004 Share Posted February 8, 2004 Idle control valve !!!!! mine seems to need the water system bleeding occasionaly and when this needs doing the idle goes strange !! Dude:flame Dev Quote Link to comment Share on other sites More sharing options...
eyefi Posted February 9, 2004 Share Posted February 9, 2004 Originally posted by Ian C Does anyone know the correct voltage output of the O2 sensor so I can check the diagnostics port with a multimeter tomorrow? it says pulse gen in the book, but thats not right, is it? i can tell u tomorrow morning, cos i just happen to have mine monitored at the moment. i dont think its the o2 though. whats the voltage at the battery? Quote Link to comment Share on other sites More sharing options...
eyefi Posted February 9, 2004 Share Posted February 9, 2004 does it happen all the time? id have a look at IDL1 and IDL2 as well. Quote Link to comment Share on other sites More sharing options...
Ian C Posted February 9, 2004 Author Share Posted February 9, 2004 Cheers Dude - I'll take the ICV fully off tonight after checking the O2 diagnostics, and soak it in something nasty overnight. As a point of interest I did have to put some coolant in the overflow tank on saturday as it was dry, perhaps I also need to bleed the system. Eyefi - IDL1 and IDL2, are they diagnostic ports or fuses?! Voltage at battery, dunno, but I can check it. It was recently charged up. -Ian Quote Link to comment Share on other sites More sharing options...
eyefi Posted February 9, 2004 Share Posted February 9, 2004 stock 02 voltage:- all over the place. generally 0.75v to 0.82v at idle (around 14.7 afr) idl1 & 2 r the throttle sensors, i dont think they r in the diagnostic port and i dont have the ecu pins to hand. it does sound like icv though. Quote Link to comment Share on other sites More sharing options...
Ian C Posted February 9, 2004 Author Share Posted February 9, 2004 Cheers Eyefi, I'll let you know the results tonight. My Apexi AFC has a link to the throttle position sensor and it's reading correctly still so I don't think it's that. Multimeter work, coolant topup, and severe cleaning of the ICV tonight then -Ian Quote Link to comment Share on other sites More sharing options...
eyefi Posted February 9, 2004 Share Posted February 9, 2004 one of them has a vacuum applied voltage test (it was this that caught my attention- probably nothing to do with this prob, but...), its listed on the ecu pin diag from the book, iirc they r the same pins in jspec. Quote Link to comment Share on other sites More sharing options...
Ian C Posted February 10, 2004 Author Share Posted February 10, 2004 Hmm - my Ox1 pin on the diagnostic port reported 0.03v when I fired the car up tonight. I swapped the O2 sensor out with another one that's known good and it still reported 0.03v. Strange. Car ran like a dog Whenever I revved it, it was pinking and rattling as the revs dropped, never mind when they fell below idle speed. I fired it up in the 0degC weather and it started running at 800rpm immediately, which is way too low. Gotta be fuelling related surely? Too lean? Some sensor gone tits up? I've got the ICV off the car and am soaking its guts in brake cleaner overnight, I've also got a spare one of those to swap in tomorrow, apart from that I guess I'm gonna have to check all the hoses AGAIN sigh. Funny how this happens just after a service. What could they have disturbed that would cause this? -Ian Quote Link to comment Share on other sites More sharing options...
eyefi Posted February 10, 2004 Share Posted February 10, 2004 Originally posted by Ian C Hmm - my Ox1 pin on the diagnostic port reported 0.03v when I fired the car up tonight. I swapped the O2 sensor out with another one that's known good and it still reported 0.03v. Strange. when hot or cold? the value i gave u was for hot, warmup phase over. does it only behave like this when the revs drop, no throttle applied or does it do it if the revs r allowed to drop with some throttle still applied? does it run fine when accelerating up the rev range? Quote Link to comment Share on other sites More sharing options...
Ian C Posted February 10, 2004 Author Share Posted February 10, 2004 When cold - I don't fancy getting the engine warm in this state as it's pinking a bit when idling now Accelerating up the rev range is peachy, it's smooth as ever. Couldn't say exactly at the moment if it chugs when easing off the throttle, I can check that once I've got an ICV plumbed back in tonight. I think what you are saying is to rev it up and then close the throttle to about 5-10% open and see if it still freaks out as the revs drop. If it runs OK like that would this point strongly at the ICV as the main suspect? Side question - why has the ICV got a coolant feed & return? It's got no temperature sensor electronics that I can find onboard or on circuit diagrams so why flow coolant through it...? Ta for your help so far -Ian Quote Link to comment Share on other sites More sharing options...
Matt Harwood Posted February 10, 2004 Share Posted February 10, 2004 Ian, I know this is very basic, but are you sure you've had the correct plugs fitted and are the plug gaps correct? Also, check the MAP sensor is fully connected. A car I saw recently, was doing some strange stuff, (although this was more like an artificial rev limit at 4k rpm), but you never know, it may have come dislodged while the car was being serviced... Quote Link to comment Share on other sites More sharing options...
eyefi Posted February 10, 2004 Share Posted February 10, 2004 i think the icv is a simple mechanical valve that needs the coolant to make it the same temp as the engine. so on cold its fully open and as the coolant warms up and the valve closes so the revs drop. I think what you are saying is to rev it up and then close the throttle to about 5-10% open and see if it still freaks out as the revs drop. If it runs OK like that would this point strongly at the ICV as the main suspect? im not sure if the icv is the only variable on throttle off, but yeah something like that. none of the throttle adjustment screws have been tampered with? do u have a spare MAP sensor? does it smoke black when it does it? Quote Link to comment Share on other sites More sharing options...
Ian C Posted February 10, 2004 Author Share Posted February 10, 2004 Originally posted by Matt Harwood Ian, I know this is very basic, but are you sure you've had the correct plugs fitted and are the plug gaps correct? Also, check the MAP sensor is fully connected. A car I saw recently, was doing some strange stuff, (although this was more like an artificial rev limit at 4k rpm), but you never know, it may have come dislodged while the car was being serviced... I got some NGKs off Alex H a while back and have had those fitted. I can't remember what model number the plugs are though. To be honest I haven't a scooby-doo what they are gapped at either. Maybe I should yank them out and check them What gap should they be at? MAP sensor check will come with a full sweep of the ECU pins with the multimeter - a tedious job but looks like it will be necessary... -Ian Quote Link to comment Share on other sites More sharing options...
Ian C Posted February 10, 2004 Author Share Posted February 10, 2004 Originally posted by eyefi i think the icv is a simple mechanical valve that needs the coolant to make it the same temp as the engine. so on cold its fully open and as the coolant warms up and the valve closes so the revs drop. im not sure if the icv is the only variable on throttle off, but yeah something like that. none of the throttle adjustment screws have been tampered with? do u have a spare MAP sensor? does it smoke black when it does it? The ICV has a big stepper motor with six wires going to it. +ve, gnd, and a switch for each direction of travel = 6 wires. Unless there is a mechanical element as well which simply reacts to coolant heat. The ICV controls idle-up for lights/aircon loads as well as just cold start. (which incidentally still works on mine, switch on lights -> idle goes up) None of the throttle adjustment screws have been moved, the original white paint blobs are unbroken. I have a spare MAP sensor, I can swap that in but as it runs fine under load I wouldn't have thought it was that. No idea about the exhaust colour, I'll check. -Ian Quote Link to comment Share on other sites More sharing options...
Matt Harwood Posted February 10, 2004 Share Posted February 10, 2004 Originally posted by Ian C Maybe I should yank them out and check them What gap should they be at? 0.8 mm IIRC. Quote Link to comment Share on other sites More sharing options...
SkyJawa Posted February 10, 2004 Share Posted February 10, 2004 Originally posted by Ian C I got some NGKs off Alex H a while back and have had those fitted. I can't remember what model number the plugs are though. To be honest I haven't a scooby-doo what they are gapped at either. Maybe I should yank them out and check them What gap should they be at? MAP sensor check will come with a full sweep of the ECU pins with the multimeter - a tedious job but looks like it will be necessary... -Ian Hi mate, I seem to remember reading when I was looking for spark plugs the the NGK's should be changed frequently. I got the Denso IK24's as supposedly the lifespan is about 30k miles or so, but I'm sure people said the NGK's need doing every service or something, but that it wasn't an issue as they were much cheaper than the Denso so it kinda evened out cost wise. Of course I could be, and most likely am, talking utter crap, but thought it worth a mention! Cheers! Quote Link to comment Share on other sites More sharing options...
Ian C Posted February 10, 2004 Author Share Posted February 10, 2004 Cheers guv but they only went in a week ago -Ian Quote Link to comment Share on other sites More sharing options...
Ian C Posted February 10, 2004 Author Share Posted February 10, 2004 Onward ever onward. All these tests were done in isolation of each other, eg I reversed the change before performing the next one. Unless I say otherwise, the engine still had trouble idling and clattered on liftoff. *I pulled the plugs and they were black with petrol glistening off them. Dunno if that's because I've been starting it and switching it off while it's cold a lot or it's overfuelling for some reason. I checked the gaps, 0.8mm all round. *I swapped them out for my old plugs, HKS S35i's, no change. *I checked the ECU error codes - none were stored. *I disconnected the O2 sensor, fired it up and it stored the correct fault (21) *I disconnected the intake temperature sensor, fired it up and it stored the correct fault (24) *The PCV pipes are in perfect condition. The PCV valve still only works one way (and sucking in cam cover air is pretty horrible, let me tell you) *The throttle position sensor is reporting correctly to the Apexi AFC *The MAP sensor is reporting correctly to the AFC *I've soaked the ISC valve overnight in brake cleaner and put it back in *I've disconnected the ISC valve and fired it up - this was the only thing so far to make a noticeable change - the rpms started out at 1400 and began climbing to 1500+, basically I lost all control of the idle (but no error codes were stored). It ran OKish at these RPMs but then it does if I manually rev it up to that anyway. *I did Eyefi's test of revving it up and easing off the throttle so the revs dropped - I *still got* the clattery preignition noises as the revs dropped. *I've removed a few harder to reach air hoses on the throttle body side, and checked the non-return valve on the EVAP line - it works So - no fault codes. That says to me that whatever is wrong it's not something the ECU monitors. This "lift-off and die" symptom, would it be caused by too much air or too much fuel? I'm running out of things to check. Gonna work through the voltage specs for the ECU pins now, which sucks, but there isn't much else to try. Why can't I have an easy problem -Ian Quote Link to comment Share on other sites More sharing options...
SkyJawa Posted February 10, 2004 Share Posted February 10, 2004 Originally posted by Ian C Cheers guv but they only went in a week ago -Ian LMFAO - that scuppered that one then! Quote Link to comment Share on other sites More sharing options...
Ian C Posted February 10, 2004 Author Share Posted February 10, 2004 I haven't fixed it yet, but I am utterly sure I've found the problem I decided to trace all the bastard air hoses using the advanced method of either removal and visual inspection or simply blowing down the damn things. And I found when I blew down one particular one I got a hissing noise elsewhere... Good news is, it was a hissing noise where there shouldn't have been according to the pressure map. Better news is that a visual inspection shows a large hole in the tube, big enough for me to see the metal prong it fits onto showing through Bad news is the location. I swear to God out of every single hose on the entire car this is the most inaccessible. If you know where this hose is, you'll know what I mean because you've been there... http://www.ian.chisholm.clara.net/pix/burstpipe1.jpg Normally I don't relax until I've put it all back together and the car is running but even I can't deny that this had *gotta* be the problem, this hole is massive. I'll post a pic of the fubar hose once I extract it... Chris Wilson, Terry Saunders, Brian Duff, Matt H, Dude, Eyefi, et al., thanks for all your help Edited to say - no wonder the second turbo wigged out that saturday morning, it must have blown a chunk out of the hose that controls the exhaust gas bypass valve at that point, causing the leak. -Ian Quote Link to comment Share on other sites More sharing options...
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