CarlT67 Posted February 11, 2008 Share Posted February 11, 2008 Half way through a slightly spirited drive on friday I noticed that my car seemed to hold right off on the power until about 5000rpm when the power felt normal again. Then when I arrived home the car idled at about 1200rpm, I've seen this before and its fixed itself so I thought noting more of it. Then yesterday after washing the car I started it and the idle was even more erratic. It was hunting between figures of 100rpm up to 1000rpm. I let it warm up at it settled high at about 1500rpm. It then worsened this morning when I started my car at about 5.15, I couldn't keep itself going, every time I released the throttle the car just stalled. Again once warm at idled fine BUT high at 1300rpm. It seems as thought the car is working in reverse, having a lower idle when cold and having a higher when hot. What could be the issue, I have tried the diagnostics codes but that doesn't even seem to work now I just get a constant engine light Please HELP...! Link to comment Share on other sites More sharing options...
tomgeer Posted February 11, 2008 Share Posted February 11, 2008 O2 sensor perhaps? I'm sure someone with more knowledge will help you out shortly mate Link to comment Share on other sites More sharing options...
CarlT67 Posted February 11, 2008 Author Share Posted February 11, 2008 O2 sensor perhaps? I'm sure someone with more knowledge will help you out shortly mate I replaced both about 9 months ago, and I didn't really notice much improvement in mpg, so could this all be pointing to the same thing...? Link to comment Share on other sites More sharing options...
Rob Posted February 11, 2008 Share Posted February 11, 2008 Mine also still idles high, I have a long thread about it, if you search under my name. I haven't resolved it yet, but will start looking again as the weather improves. Link to comment Share on other sites More sharing options...
Rob Posted February 11, 2008 Share Posted February 11, 2008 I've also noticed of late, a power surge at 5000rpm but I'm running it with the 2nd cat in, as I never got to change it out again after my MOT, as I was sick of jacking up the car. I presume this is the two stage air plenum butterfly operating, but it seems more noticable with the cat back in. I've experienced the rapid hunting as well, when I disconnected something. Trouble is I can't remember what I disconnected. It wasn't the TPS or the IAC. Link to comment Share on other sites More sharing options...
CarlT67 Posted February 12, 2008 Author Share Posted February 12, 2008 I've also noticed of late, a power surge at 5000rpm but I'm running it with the 2nd cat in, as I never got to change it out again after my MOT, as I was sick of jacking up the car. I presume this is the two stage air plenum butterfly operating, but it seems more noticable with the cat back in. I've experienced the rapid hunting as well, when I disconnected something. Trouble is I can't remember what I disconnected. It wasn't the TPS or the IAC. That would be good, if you could remember what it was that you removed, as this could be what has happened to mine. I have a spare throttle body with the sensors mounted on it from miko_supra's n/a engine which ran fine, I am going to give that a try on friday. Link to comment Share on other sites More sharing options...
Rob Posted February 12, 2008 Share Posted February 12, 2008 Ooh, found this, actually by me... Mine did the hunting thing, like you have described when I ran it without the IAC valve fitted, basically way too much air is running in, so it overfuels (black smoke) and then the ECU cuts it to save teh engine. It would do this cycle every 1-2 seconds. Do a search for IAC valve and there'll be a description of how to test it with a multimeter. the sensor you descibe sounds like the IAC, it should say Idle Control on it. If you try to remove it, soak the two cross-head bolts in plenty of penetrant before you even try to move them, else you mash up the bolt head and you'll have to remove the whole throttle body to cut a groove in the head. Be careful, you'll probably want to remove the plastic cam cover first. So it could be that your IAC vavle is stuck fully open? these are the resistences you should be getting... I measure the resistance from the IAC valve: B1 to S3-S1 = 20 Ohm;; B2 to S2-S4 = 20 Ohm;; B1 to S4-S2 = B2 to S3-S1 = 250Ohm;-450Ohm; (not stable). On Supra repairs book, they measure 18-24Ohm; from B1 (or B2) to others. I check for a clicking sound immediately after stopping the engine and it’s OK. My question: What resistance do you get, from your IAC Valve, on your Supra? Do you hear a clicking sound when the engine is cold? You'll have to search yourself for the pinouts location to do the test. Check all your hoses too. Link to comment Share on other sites More sharing options...
CarlT67 Posted February 12, 2008 Author Share Posted February 12, 2008 Ooh, found this, actually by me... So it could be that your IAC vavle is stuck fully open? these are the resistences you should be getting... You'll have to search yourself for the pinouts location to do the test. Check all your hoses too. Thanks matey.... I do also have the feeling that something is stuck open, as when I start it I have to give it a little help to stay idle (applying throttle) for a sort amount of time then it will self idle, however as I mentioned before it doesn't idle at the correct rpm. Hope its as simple as that... Link to comment Share on other sites More sharing options...
Guest JayRA Posted February 13, 2008 Share Posted February 13, 2008 Let me know how you get on with this mate, mine has started doing exactly the same thing over the last week or so. Went away for a few weeks, and this started when i got back Anyway good luck, i'll let you know if i get it resolved. J Link to comment Share on other sites More sharing options...
CarlT67 Posted February 13, 2008 Author Share Posted February 13, 2008 OK dude Link to comment Share on other sites More sharing options...
CarlT67 Posted February 15, 2008 Author Share Posted February 15, 2008 Right I removed and fitted Miko's throttle body. One starting this made the car hunt for idle and once revved slightly stuck the revs at 3000 rpm. So what ever happened between removal from his engine and fitment to mine broke the sensors. I then re installed my original throttle body and the car started (it was warm so no probs) but idled high 1100rpm. So I thought I would have a go at mechanically adjusting the idle using the throttle stops. This made know difference to the idle rpm even when I completely removed the bracket and the throttle was wound right of the car continued to idle at 1100rpm. So the idle control valve thingy is setting the idle there... My two questions are now.... How do I adjust where the idle control valve where it holds the idle.... ...and secondly the 'not idling when cold' problem must be due down to the automatic coke system. Could anyone share any light on the system....? Link to comment Share on other sites More sharing options...
CarlT67 Posted February 16, 2008 Author Share Posted February 16, 2008 I have further investigated today and found that having the ICV plugged in or not makes no difference to the idle level or cars running. I then thought I would do the resistance check on the ICV which is detailed in the US maintenance ADF file manual. All results were 23ohms which is fine... Then checked whether there was continuity between the connector plug and the ECU pins this was also fine. Now I believe the problem must lay in either the ICV valve or the ECU, I think the problem is most likely to be in the ICV and not the ECU. I have read how to do a test on the ICV opening and closing using battery power but now have the trouble of having to remove the two screws which hold it together which are stuck solid...! Could there also be a possibility of a faulty engine temperature sensor or is there only one and it also feeds the dash temp gauge as this works fine..? Thanks Carl Link to comment Share on other sites More sharing options...
CarlT67 Posted February 17, 2008 Author Share Posted February 17, 2008 I have managed to remove the idle control sensor (ICV) and gave it a clean. On reinstalling the car started to hunt for an idle going between 1000rpm to 2500rpm repeatedly and violently. I then removed the plug and started the car again and there was no difference to the idle, still hunting in the same manor. I then removed idle control valve and started the car, this ran the same as before idle hunting. So the ICV is doing nothing. The valve works by driving a plug type fitting (via a electronic motor) into a hole in the side of the throttle body which is constantly sucking. When the car is runnig and I plug the hole the car dies, NO idle, when left wide open the car Hunts for idle agian. When the plug is half covered the car idles smoothly and depending on how much it is plugging the hole is what controls the idle rpm level. So I have managed to whittle the problem down to either the idle control valve is not working, the plug between the two is knacked or the ecu is not sending the signal. I have managed to take apart a spare ICV I had (miko's) and setting it to half block the hole so the car idles, when warm at 900rpm. Is it likely that the ECU is broken and not sending the signal or is it more likely to be the ICV valve and/or plug....? Thanks Link to comment Share on other sites More sharing options...
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