SEDGE Posted August 15, 2005 Share Posted August 15, 2005 When i start the car from cold everything runs fine but once it gets hot i notice a small misfire on tickover. Thought it may be the plugs so i put some new denso iridiums in it but still have the same problem. Any ideas on where i should start looking next ?? Quote Link to comment Share on other sites More sharing options...
penguin Posted August 15, 2005 Share Posted August 15, 2005 coil packs ... i had the same problem... and it got a lot worse! Quote Link to comment Share on other sites More sharing options...
penguin Posted August 15, 2005 Share Posted August 15, 2005 BUT..... before you do that, check the gapping on the plugs... if your BPU, should be 0.8mm Quote Link to comment Share on other sites More sharing options...
geoffvalenti Posted August 15, 2005 Share Posted August 15, 2005 I'd do a compression test next to hopefully eliminate burnt valves etc. If thats OK, I suppose you've got to start looking at injectors and coil packs, none of which are easy to see whether they work or not. Do you know which cylinder the misfire is on? Quote Link to comment Share on other sites More sharing options...
SEDGE Posted August 15, 2005 Author Share Posted August 15, 2005 The car is running standard other than a hks induction kit. Dont know which cylinder has got the miss. just checked the denso box and these are gapped a 0.4mm,would that be to small for a standard car ?? Quote Link to comment Share on other sites More sharing options...
geoffvalenti Posted August 15, 2005 Share Posted August 15, 2005 Yeah, 0.4 is a bit small 0.8 for bpu and Toyota say 1.1 standard Quote Link to comment Share on other sites More sharing options...
mikeyh Posted August 15, 2005 Share Posted August 15, 2005 I'd do a compression test next to hopefully eliminate burnt valves etc. If thats OK, I suppose you've got to start looking at injectors and coil packs, none of which are easy to see whether they work or not. Do you know which cylinder the misfire is on? id definatly do a compression test i had exactly the same problem it turned out to be number five piston was down hopfully not the prob with yours but better to be safe than sorry Quote Link to comment Share on other sites More sharing options...
SEDGE Posted August 15, 2005 Author Share Posted August 15, 2005 i've been reading the faq about plug gaps and it says not to adjust iridiums because of damaging them..can anyone confirm this ??? Quote Link to comment Share on other sites More sharing options...
Ian C Posted August 15, 2005 Share Posted August 15, 2005 It won't be your coil packs, they can be seriously buggered and the car will still idle fine and drive off boost as well. 0.4mm plug gap sounds really rather too little. The iridiums should be pregapped to 0.8mm though What state were your old plugs in - coated in blackness? Also, how big is this misfire...? Every now and again the idle will give a slight dip, it's part of the self-learning 'closed loop' system... -Ian Quote Link to comment Share on other sites More sharing options...
Jake Posted August 15, 2005 Share Posted August 15, 2005 Sedge, you said you got the 0.4 gap from reading the Denso plug box, right? (Not from actually measuring the gap.) That's odd. It sounds like a much smaller gap than we would usually see. Don't try to regap them though. I've read that you can't regap Iridium plugs without damaging them. Not 100% sure how true this is though but I wouldn't risk it. What grade of plugs are the current ones and the previous ones? Too cold a plug will not promote good idling. Personally, for £10 I would just put a set of NGK BCPR7ES in the car and see how it is then. Quote Link to comment Share on other sites More sharing options...
Matt Harwood Posted August 15, 2005 Share Posted August 15, 2005 I've had an intermittent misfire at idle ever since I've owned this Supra. Mines fine whilst driving and on full boost, right up to 1.8 bar, but it still misses at idle. I know what it's not; Spark plugs, gaps, coil packs, coil pack plugs, coil pack wiring polarity, ignitor pack, ECU, valves, compression, injectors, fuel pressure, fuel type, earth connections... But I don't know what it is. If it's any consolation, I've heard loads do it, at various states of tune. You're not alone, but if anyone knows the answer, please tell! Quote Link to comment Share on other sites More sharing options...
Ian C Posted August 16, 2005 Share Posted August 16, 2005 Well can you tell me how bad a misfire it is as at the moment I reckon it's just the closed loop system doing it's intermitten 'prod' to see if it can get away with less fuel. This is exacerbated by bigger injectors and airflow mapping... -Ian Quote Link to comment Share on other sites More sharing options...
SEDGE Posted August 16, 2005 Author Share Posted August 16, 2005 its not a big misfire its more of a small but noticable one..you can feel it when in the car and hear it through the backbox when outside (standard pipe). the plugs i took out are ngk bcp7ev and look like they were running fine and the new ones are ik24's. after doing some more research im now thinking they should have been ik20's on a stock supra ??? Quote Link to comment Share on other sites More sharing options...
Matt Harwood Posted August 16, 2005 Share Posted August 16, 2005 Well can you tell me how bad a misfire it is as at the moment I reckon it's just the closed loop system doing it's intermitten 'prod' to see if it can get away with less fuel. This is exacerbated by bigger injectors and airflow mapping... -Ian Mines been there from the day I got the car. I wouldn't have thought anything of it if my previous one hadn't been so smooth in comparison. The miss is exactly as Sedge describes it. It's probably only one cylinder every now and again. It can go for two or three seconds without missing a beat, but on the other hand, it can do it more frequently. Quote Link to comment Share on other sites More sharing options...
merckx Posted August 16, 2005 Share Posted August 16, 2005 after doing some more research im now thinking they should have been ik20's on a stock supra ??? That's correct. But the IK24's are okay to use aswell, you shouldn't have any problems with the plugs especially when the car is idling unless the gap is way out. Quote Link to comment Share on other sites More sharing options...
Alex Posted August 16, 2005 Share Posted August 16, 2005 Mine bumps now and again...due to hunting for 14.7:1 it's the ecu doing it...nothing untoward. Bless the ECU it's always trying to use less fuel I can make mine really noticable by trimming the fueling back by a couple of % from ideal. Also the 0.4 on the packet fo the Iridiums is the DIAMETER of the electrode NOT THE GAP. The gap is 0.8 on IK24's unless it's been messed about with. Quote Link to comment Share on other sites More sharing options...
penguin Posted August 16, 2005 Share Posted August 16, 2005 It won't be your coil packs, they can be seriously buggered and the car will still idle fine and drive off boost as well. 0.4mm plug gap sounds really rather too little. The iridiums should be pregapped to 0.8mm though What state were your old plugs in - coated in blackness? Also, how big is this misfire...? Every now and again the idle will give a slight dip, it's part of the self-learning 'closed loop' system... -Ian I had a heaving mass of missfires on mine, on idle/offboost and onboost..., changed the coil pack that was missfiring, and problem solved... Quote Link to comment Share on other sites More sharing options...
Matt Harwood Posted August 16, 2005 Share Posted August 16, 2005 In an attempt to give you an idea of its frequency, in binary form, it goes something like this... 1111011111101111101111101111101111011111011111011110111011101111101111011111101110111011011111101110 LOL! I'm sure thats far more frequently than an ECU trying to do it's stuff. Quote Link to comment Share on other sites More sharing options...
Ian C Posted August 16, 2005 Share Posted August 16, 2005 I had a heaving mass of missfires on mine, on idle/offboost and onboost..., changed the coil pack that was missfiring, and problem solved... That might have actually been a bad connection to the coil Based on observation of this forum and personal experience, those connectors can get a bit loose over time and emulate a bad coil pack. I had a set that were so bad once that 0.1bar of boost misfired, and yet off boost and idle were fine still - surely yours hadn't degraded past that? (although I'm ready to be corrected!) -Ian Quote Link to comment Share on other sites More sharing options...
Ian C Posted August 16, 2005 Share Posted August 16, 2005 In an attempt to give you an idea of its frequency, in binary form, it goes something like this... 1111011111101111101111101111101111011111011111011110111011101111101111011111101110111011011111101110 LOL! I'm sure thats far more frequently than an ECU trying to do it's stuff. Well if that's accurate then it's your 5th cylinder -Ian Quote Link to comment Share on other sites More sharing options...
penguin Posted August 16, 2005 Share Posted August 16, 2005 That might have actually been a bad connection to the coil Based on observation of this forum and personal experience, those connectors can get a bit loose over time and emulate a bad coil pack. I had a set that were so bad once that 0.1bar of boost misfired, and yet off boost and idle were fine still - surely yours hadn't degraded past that? (although I'm ready to be corrected!) -Ian could well of been the case, although i'm still using the same connectors.... the car has just under 100k miles.... i've got the old coil pack if anyone wants to have a gander.... Quote Link to comment Share on other sites More sharing options...
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