Ned Posted July 31, 2011 Share Posted July 31, 2011 As requested, here is a tech thread about my issues. So the problem is that the LS400 i bought can't do skids and uses an obscene amount of fuel. A suggestion was that the temp sensor is shit and is measuring a cold engine all the time and over fueling and limiting power. Replaced it last Friday and it still wouldn't do a skid. Apparently i should re-set the ECU after i replac the temp sensor so disconnected the battery lead for 5-10 min but that didn;t fix it either. Found out on Sunday that it will do a skid when cold so here comes the next stage in fault finding... From Spam thread; What sensors are normally ignored by 1UZ ECU when cold? aka, does it ignore the O2 sensors until they get up to temp and only then start taking into account what they read?Thinking this is what could cause my car to run sweet when cold but shit when warm... Yea ned they ignore the o2 readings until warm, but they will be heated so that doesnt take longTried By passing the fuel pump controller yet? and checked the AFM? Did you try unpluging the AFM? I'd start there. Could try buning in a spare ECU? although if that was faulty I would have though fancy lexus self diagnostics would have noticed and let you know with lack of burnouts/warning light. Did you try unpluging the AFM? I'd start there. No, i did not. What should happen when i do this? Still not quite sure? Should i just unplug it and see if theres a change and if theres a change it works and if no change it's fucked? or is there a specific thing i'm looking for? When you unplug the AFM it just runs on some preset super conservative rich maps based on TPS and rpm. So if it runs better with it unplugged it means its sending BS signals to the ECU causing your shit running hey Ned, since were not using your car thread to discuss your car problem ill put this information in here so it gets lost forever,the O2 sensors arnt heated, they are single wire narrow band so they could be causing your issue. but unplug the AFM (when its hot) and see what happens. if you get you tyre smoking ability's back then its probably the AFM ay? Cheers Sheepers. There was just some discussion that maybe the ECU makes up it's own mind when it's cold and only listen to the sensors once the car is warm etc. Any merit to this? Cheers Sheepers. There was just some discussion that maybe the ECU makes up it's own mind when it's cold and only listen to the sensors once the car is warm etc. Any merit to this? no If you are worried about sensors fucking things up, get the factory toyota service manual, and spend a arvo checking them all with a meter/scope. Should rule things out pretty quickAs people have said though the AFM and fuel pump controller are a good place to start So things to try; -reset ECU again by disconnecting battery for 1/2 the day. -unplug AFM when warm and see if theres a difference -test O2 sensors etc with meter according to service manual Moar? Quote Link to comment Share on other sites More sharing options...
Spencer Posted July 31, 2011 Share Posted July 31, 2011 Reseting the ECU wont do shit. Add to your list running a temporary full 12V supply to the fuel pump, if other things dont work Pretty much jusrt get the service manual and roll through the trouble shooting page, it has specs for all sensors and shit Quote Link to comment Share on other sites More sharing options...
felixx Posted July 31, 2011 Share Posted July 31, 2011 umm take it to Mr Lexus and plug it into their diagnostics machine Quote Link to comment Share on other sites More sharing options...
Spencer Posted July 31, 2011 Share Posted July 31, 2011 ^ umm waste of time Its not OBD-2 or anything flash like that, just jumpering TE1 and E1 in the diagnostic port will flick you any error codes it has Quote Link to comment Share on other sites More sharing options...
Spencer Posted July 31, 2011 Share Posted July 31, 2011 Oh there is a test mode you can chuck these ECU's into which can help find intermitent sensor issues. You jumper TE2 and E1 and go for a drive until its warm (ie where the fault is happening) you can then jumper TE1 and E1 and see if the test mode has flicked any codes that dont normally show up. Get the manual though as I cant remember the exact steps! You can also check the o2 sensors output at the diagnostic terminal (OX1, OX2 i think), and use the Vf terminal to see how much the ECU is actually using the sensors to compensate for any long term lean or rich condition. Quote Link to comment Share on other sites More sharing options...
Ned Posted July 31, 2011 Author Share Posted July 31, 2011 Cheers dude Will give that all a go and hope for the best Quote Link to comment Share on other sites More sharing options...
UTERUS Posted August 1, 2011 Share Posted August 1, 2011 Also, unless i'm thinking of something else, jumping TE1 and E1 will bypass the fuel pump ecu and give the pump full voltage all the time. Which will tell you if the fuel pump ecu is fucked. Quote Link to comment Share on other sites More sharing options...
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