ronttuk Posted January 30, 2012 Share Posted January 30, 2012 My uk spec supra basically std has stalled a cpl of times if i give it a little throttle to say go across a t junction its happened 3 times now any ideas what to look for ?? Quote Link to comment Share on other sites More sharing options...
Guigsy Posted January 30, 2012 Share Posted January 30, 2012 Has the battery been unplugged recently? Mine done this when the ecu relearns. Once iv driven the car a bit and its been turned off it's then fine. Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted January 30, 2012 Share Posted January 30, 2012 I used to get that when i first got my Supra, turned out to be the std trac control cutting in. Quote Link to comment Share on other sites More sharing options...
Nic Posted January 30, 2012 Share Posted January 30, 2012 Just an idea, does it have an aftermarket BOV fitted? Quote Link to comment Share on other sites More sharing options...
caseys Posted January 30, 2012 Share Posted January 30, 2012 Just an idea, does it have an aftermarket BOV fitted? MAF with BOV? I'm with you on that. What happens if you've got the throttle on and suddenly take your foot off it? Do the revs dip then stall/recover sometimes? Quote Link to comment Share on other sites More sharing options...
johnny g Posted January 30, 2012 Share Posted January 30, 2012 Thread title changed. Can you please use meaningful thread titles, especially in MkIV Technical. Thanks. Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted January 30, 2012 Share Posted January 30, 2012 Trouble is "give it a little throttle " means different things to different people, especially on here;) Quote Link to comment Share on other sites More sharing options...
ronttuk Posted January 30, 2012 Author Share Posted January 30, 2012 yes it has a BOV so what could be wrong with the BOV ? It stalls when pulling away as I take my foot off the throttle or just give it less gas the turbos are not usually spooling at that point. Casey says MAF whats the MAF is that the bit between the air filter and the inlet manifold ?? What could be wrong with that ? tomoorow ill do a fault code test see what it comes up with Quote Link to comment Share on other sites More sharing options...
Scott Posted January 30, 2012 Share Posted January 30, 2012 yes it has a BOV so what could be wrong with the BOV ? It stalls when pulling away as I take my foot off the throttle or just give it less gas the turbos are not usually spooling at that point. Casey says MAF whats the MAF is that the bit between the air filter and the inlet manifold ?? What could be wrong with that ? tomoorow ill do a fault code test see what it comes up with It isn't the BOV that's faulty as such, it's more the BOV causing the issue as the ECU is expecting more air than it is seeing... thus overfueling and stalling. What BOV do you have? Some are less likely to do it than others. Quote Link to comment Share on other sites More sharing options...
Nic Posted January 30, 2012 Share Posted January 30, 2012 Casey says MAF whats the MAF is that the bit between the air filter and the inlet manifold ?? What could be wrong with that ? tomoorow ill do a fault code test see what it comes up with The UK Supra is fitted with a MAF/Mass Air Flow sensor, this tells the cars ECU how much air is going to the engine, the ECU then adjust the fueling mix accordingly. When you lift off the throttle a vent to atmosphere BOV releases some of this air from the system causing a rich air/fuel mixture ie. too much fuel, which can cause the car to stall. This is only a problem with the UK Supra, the J-spec Supra uses a MAP/Manifold Absolute Pressure sensor which is not effected by a vent to atmosphere BOV. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted January 30, 2012 Share Posted January 30, 2012 This may help you see what's wrong. It's Skyline experience based, but applicable here, too. It's part of my posts to a thread to another forum from 14 years back, so just read the gist of it. The following is based on my Skyline experience, with air usage measured by air flow meters before the turbos. It is not applicable to cars that soley use a MAP sensor and throttle angle for air measurement . To recap I put in a bigger intercooler and the standard Skyline duct that runs across the lower front of the car taking dumped air from the 2 blow off valves to the intake between the air flow meters and the twin turbo inlets was masking air exiting the lower 4 rows of the new IC. Having spent a good deal of money on this item it pained me to see some of effectively blanked off. So I decided to blank the inlet off altogether where the cross pipe entered the turbo inlet ducting, remove the cross pipe and vent to atmosphere. The dump valves were being held open at idle by the idle vacuum level, so after ages of pondering i made a set up of solenoids to control when vacuum was applied to the dump valves. This set up worked perfectly. *HOWEVER* a much more serious problem occurred, which any similarly inducted turbo car will potentially suffer if the boost air is dumped to atmosphere rather than as standard into the air intakes after the AFM (s). On the overrun, after a period of boost running, the standard set up will recirculate the excess boost back into the turbos, through the IC, and back through the dump valves to the turbo inlet again until the turbos inertia has slowed them to the point of little or no boost. The AFM's do not see any more air entering the engine, as it is being recirculated. However, when we dump to atmosphere, that air is lost from the system and the turbos draw in fresh air via the AFM (s). This causes the engine to go mad rich, as the throttles are closed and no fuel is really needed. Hence the black smoke seen on the overrun after my mods. Worse still was a noticeable but very short period of detonation when coming hard back on the throttle. This puzzled me totally, then it dawned. As the fuel system started working normally again the Lambda sensor "caught up" with what was happening, saw a very overly rich mixture, and shut down the injector pulse width, creating a very lean mixture, causing a brief, but very dangerous period of detonation! I spent the afternoon and evening making new bracketry for the IC, new hoses and adaptors and shifting the IC forward that critical 40 mm or so, enabling me to fit the original moulded duct from the BOV's behind the IC without blocking it. Quite a lot of work and fabrication... However, the mod I was planning could well have caused damage, and is certainly something to be very aware of if one has a similar AFM pre turbo set up changed to dump boost to atmosphere. The type of BOV matters not, it's the fact that the air no longer re circulates but is lost from the system, confusing the AFM (s) into thinking the engine is wanting more air/fuel mixture. An oscilloscope on the O2 sensors confirmed what was happening. We live and learn, often the hard way, but in this case not as hard a lesson as it might have been. I hope this helps, I searched the web long and hard for references to BOV problems, and failed to find any details of why dumping to atmosphere on none MAP sensor systems, that aren't mapped for this, is potentially dangerous. I can now finally make some proper seals to make sure all air entering the radiator ducting passes through the IC, something HKS totally fail to address, at the moment most air will go around rather than through the IC core. Quote Link to comment Share on other sites More sharing options...
ronttuk Posted January 31, 2012 Author Share Posted January 31, 2012 The BOV is a HKS 1 Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted January 31, 2012 Share Posted January 31, 2012 Stock recirc valve back on, problem sorted Quote Link to comment Share on other sites More sharing options...
Scott Posted January 31, 2012 Share Posted January 31, 2012 The BOV is a HKS 1 One, not 1 As above, if you don't want the hassle either just ditch the aftermarket BOV in favour of a stock one or fit the recirculating attachment to the HKS. If you really want the aftermarket type then I would look at a different model as yours is leaking a bit by the sounds of it (if it's just at low revs this is happening). Quote Link to comment Share on other sites More sharing options...
ronttuk Posted January 31, 2012 Author Share Posted January 31, 2012 thanks guys ill have a look at it when the weather warms up Quote Link to comment Share on other sites More sharing options...
chrispot Posted February 1, 2012 Share Posted February 1, 2012 This may help you see what's wrong. It's Skyline experience based, but applicable here, too. It's part of my posts to a thread to another forum from 14 years back, so just read the gist of it. The following is based on my Skyline experience, with air usage measured by air flow meters before the turbos. It is not applicable to cars that soley use a MAP sensor and throttle angle for air measurement . To recap I put in a bigger intercooler and the standard Skyline duct that runs across the lower front of the car taking dumped air from the 2 blow off valves to the intake between the air flow meters and the twin turbo inlets was masking air exiting the lower 4 rows of the new IC. Having spent a good deal of money on this item it pained me to see some of effectively blanked off. So I decided to blank the inlet off altogether where the cross pipe entered the turbo inlet ducting, remove the cross pipe and vent to atmosphere. The dump valves were being held open at idle by the idle vacuum level, so after ages of pondering i made a set up of solenoids to control when vacuum was applied to the dump valves. This set up worked perfectly. *HOWEVER* a much more serious problem occurred, which any similarly inducted turbo car will potentially suffer if the boost air is dumped to atmosphere rather than as standard into the air intakes after the AFM (s). On the overrun, after a period of boost running, the standard set up will recirculate the excess boost back into the turbos, through the IC, and back through the dump valves to the turbo inlet again until the turbos inertia has slowed them to the point of little or no boost. The AFM's do not see any more air entering the engine, as it is being recirculated. However, when we dump to atmosphere, that air is lost from the system and the turbos draw in fresh air via the AFM (s). This causes the engine to go mad rich, as the throttles are closed and no fuel is really needed. Hence the black smoke seen on the overrun after my mods. Worse still was a noticeable but very short period of detonation when coming hard back on the throttle. This puzzled me totally, then it dawned. As the fuel system started working normally again the Lambda sensor "caught up" with what was happening, saw a very overly rich mixture, and shut down the injector pulse width, creating a very lean mixture, causing a brief, but very dangerous period of detonation! I spent the afternoon and evening making new bracketry for the IC, new hoses and adaptors and shifting the IC forward that critical 40 mm or so, enabling me to fit the original moulded duct from the BOV's behind the IC without blocking it. Quite a lot of work and fabrication... However, the mod I was planning could well have caused damage, and is certainly something to be very aware of if one has a similar AFM pre turbo set up changed to dump boost to atmosphere. The type of BOV matters not, it's the fact that the air no longer re circulates but is lost from the system, confusing the AFM (s) into thinking the engine is wanting more air/fuel mixture. An oscilloscope on the O2 sensors confirmed what was happening. We live and learn, often the hard way, but in this case not as hard a lesson as it might have been. I hope this helps, I searched the web long and hard for references to BOV problems, and failed to find any details of why dumping to atmosphere on none MAP sensor systems, that aren't mapped for this, is potentially dangerous. I can now finally make some proper seals to make sure all air entering the radiator ducting passes through the IC, something HKS totally fail to address, at the moment most air will go around rather than through the IC core. my supra has a afm fitted and a vent to atmosphere dump valve and has no problems with stalling, what you said above makes sense, but i thought it would be ok as after a period of boosting then letting of the throttle the injectors shut down on the over run until about 1500 rpm or so?, or a i missing somthing. regards chris Quote Link to comment Share on other sites More sharing options...
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