Guest bastaad525 Posted November 5, 2003 Share Posted November 5, 2003 okay, more EFI ignorance for me... I miss my SU's okay I want to know, exactly what the TPS does. I mean, I know what it does in a turbo zxt setup it only has two positions, 'open' and 'closed', closed being idle, and open being anything else. but what I dont know is what the ECU does with this information. What does it do so differently when the TPS tells it that the throttle is at the idle position? I disconnected mine last night, to see if it would cure the serious bog that would occur right when you start to push on the throttle (just for a second, then it would continue to rev as normal, was most noticeable between quick shifts). Sure enough, it cured it... now there is no bog or stumble off idle like there was... I figured a faulty TPS but I did have it tested and it is working okay it seems and is adjusted properly. But... the car runs better with it disconnected. The idle did change a bit but I can't say for better or for worse, it got a little higher but seems as smooth as it was before. So, before I go running around with it disconnected, which by the way the car seems to run fine w/o it, so I'm not too worried about it... but it just got me thinking, what is the ECU not doing any more because of it? What, if any, are the potential problems? Quote Link to comment Share on other sites More sharing options...
Guest ZmeFly Posted November 5, 2003 Share Posted November 5, 2003 when i was adjusting mine i did take the cover off just to see what was happening in there. when you set it up properly it will be resting on the right contact, looking at it from the drivers side of course, just partly on throttle, i would say cruising, it rests in the middle of the two contacts and just a little further then that it rests on the left contact. its a very simple device when you look at it. works mechanically. if you are having some stumble off idle and or in between shifts if you havent done it already i would suggest adjusting the afm slightly. i had a horrible problem with this happening to me and an adjustment of about 12 teeth fixed this problem for the most with my car. good luck, james Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted November 5, 2003 Share Posted November 5, 2003 I was thinking AFM too, but again, it definately seems to follow the movement of the TPS. I also took the cover off of it and watched it... start moving the throttle, as soon as the middle switch stops touching the contact the motor will bog, just for an instant... really badly though, like a bad cough. If I disconnect the TPS it doesn't do it at all, so I dont see it being the AFM. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted November 7, 2003 Share Posted November 7, 2003 anyone? I'm still running w/o the TPS connected and the car runs good still, no more sign of that cough... but I would really like to know what exactly the ECU does when the TPS is closed so I know what effect disconnecting it is having. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted November 7, 2003 Share Posted November 7, 2003 As far as I know, the switch closure merely tells the ECU to use the idle map to run the engine. That should mean no ignition advance, and a lean, limited fuel map. Obviously the engine should run better with the idle switch open - it's designed to. If it won't idle properly with the switch closed, there may be something misadjusted, but why worry about it? It's just another emissions device, and if it's not working, why use it? Quote Link to comment Share on other sites More sharing options...
BayAreaZT Posted November 7, 2003 Share Posted November 7, 2003 Maybe this will help you out http://www.hammondsplains.com/zclub/techtips/tps/index.html Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted November 7, 2003 Share Posted November 7, 2003 Maybe this will help you outhttp://www.hammondsplains.com/zclub/techtips/tps/index.html When reading this, keep in mind it applies to the factory Z. The ECCS used in 280ZXT and Z31 is different in that it doesn't use a WOT contact, and needs no tachometer input (the ECCS controls the ignition using a crank angle sensor). Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted December 13, 2003 Share Posted December 13, 2003 okay wait... is the EFI supposed to run more LEAN with the TPS closed in the idle position, or more RICH? I know it definately idles smoother with it connected, I would think that means leaner mixture? I'm still debating leaving it connected or not, if only as a function of getting a little better gas mileage (I do spend a lot of time at idle). Also I know now w/o a shadow of a doubt what's happening to cause the off idle hiccup when the TPS is connected, and goes open. With the TPS connected and in the idle position, the ignition timing is steady at 20* BTDC, as soon as the TPS goes open, timing immediately jumps/retards to about 14* BTDC. I still haven't found the reason why it does this.... so you guys think leaving connected or not will effect my fuel consumption either way? Quote Link to comment Share on other sites More sharing options...
Bernardd Posted December 13, 2003 Share Posted December 13, 2003 The afm is set very lean from factory. You can get rid of the bog by increasing static fuel pressure, loosening the afm door a bit, closeing the idle bypass a bit (I never tried that one but it should work) and my personal favorite.....switching to the z31 ecu. All your posts about the quirks and generally annoying behaviour of the stock electronics sums up why I switched. I was never able to get it to run to my satisfactioniin all situations. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted December 13, 2003 Share Posted December 13, 2003 Heh... funny you should say that... I dont think I'll ever get it to perform to my satisfaction either... 3 damn 280ZX's I've owned now and all 3 of them with quirky EFI's that refuse to be sorted. Quote Link to comment Share on other sites More sharing options...
paul vixie Posted June 6, 2010 Share Posted June 6, 2010 on another thread i asked this same question and eventually went page by page on the FSM and found that there is a timing advance (of about 10 to 15 degrees) when the TPS indicates that the car is idling, or when the CHTS indicates that the car is cold. over in zdriver, nismopick said that the timing should be set with the TPS disconnected. this means if you set timing with the TPS plugged in you're doing it on an advanced basis, and when you lose the "idle advance" coming off idle then it'll look like retard. i'm going to get out there and set my timing with the engine warm, having cleaned the CHTS and knock sensor contacts, and set the base timing without the ~10 degree advance that gets added at idle, and i'll let you know how it goes. Quote Link to comment Share on other sites More sharing options...
paul vixie Posted August 26, 2010 Share Posted August 26, 2010 i'm going to get out there and set my timing with the engine warm, having cleaned the CHTS and knock sensor contacts, and set the base timing without the ~10 degree advance that gets added at idle, and i'll let you know how it goes. and indeed, all is now well with engine timing wrt the TPS. thanks for all who contributed material to these threads. Quote Link to comment Share on other sites More sharing options...
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