Dave Carroll Posted May 4, 2015 Share Posted May 4, 2015 Gents, As perfectly as my new toy runs 99.9% of the time, I was warned by the previous owner sometimes it will have a misfire when starting when warm. Today I got my first taste of this... Been out all day enjoying the car on this sunny Bank holiday, mixture of mountain / B roads, motorway cruising and an unfortunate traffic jam in the hot sun. Didn't miss a beat. But, couple hours after getting back and the car cooling, go to start it up, and it won't start first turn of the key, second turn it fired with a misfire. Left it another couple of hours, go back out to start it up again, temp gauge reading just above cold now, and again won't start. Second turn, starts with some trouble (had to hold the throttle open) but once running, not missing a beat again. Took for a drive, pulled like a train as always. Strange, anyone got any suggestions for possibly heat soak related misfire / starting trouble? Car has new spark plugs and coil pack clips. Not looked at the packs themselves yet, so I guess next step. Curious if anyone has any experience of heat related issues. Car is BPU with HKS F Con, so curious if this could be the source of the problem. Cheers Dave Quote Link to comment Share on other sites More sharing options...
Benjy Posted May 4, 2015 Share Posted May 4, 2015 When you say a misfire, do you mean once it's fired up from the 2nd turn of the key it runs as if it's dropped a cylinder, or is it just poor warm starting? Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted May 4, 2015 Share Posted May 4, 2015 Are you sure its not down to a failed ECU coolant temp sensor, this can cause permanent slightly rich mixture, which in turn can cause bad hot start due to too much fuel. Quote Link to comment Share on other sites More sharing options...
Benjy Posted May 4, 2015 Share Posted May 4, 2015 Are you sure its not down to a failed ECU coolant temp sensor, this can cause permanent slightly rich mixture, which in turn can cause bad hot start due to too much fuel. This was my thinking. Or a crank sensor. Quote Link to comment Share on other sites More sharing options...
T14PPA Posted May 4, 2015 Share Posted May 4, 2015 My guess would be crank sensor as only happens when warm or hot Quote Link to comment Share on other sites More sharing options...
chrispot Posted May 4, 2015 Share Posted May 4, 2015 could be a fuel pressure problem. i have had this issue with a hot start and warm restart ( on a mk3 turbo), where the fuel pressure in the fuel rail drops due to either the regulator or fuel pump one way valve and the fuel pressure drops which causes the fuel to boil so to speak in the fuel rail, and when you go to restart the engine there is only vapour in the fuel rail. toyota put on a vsv connected to the fuel pressure regulator vac/pressure pipe to vent the pipe on the regulator to increase fuel pressure (stops the regulator from seeing vac) when the engine is being started i don't know how long it's keep on for once started. to my knowledge it's only ever operated when the engine is warm/hot. i had a led connected to mine to monitor it and had only ever seen it operate once for a short time. my problem on the mk3 turbo was the fuel pressure regulator, it did not hold pressure long enough to stop the fuel from getting a vapour lock. it only ever was a problem in hot weather after a longish run. change it back to a std reg, problem sorted. i am not saying it's your regulator, because the toyota one is very good, it could be the fuel pump check valve. just something it could be? regard chris. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted May 4, 2015 Share Posted May 4, 2015 Are there any fault codes stored? What is none stock about the car? Quote Link to comment Share on other sites More sharing options...
Dave Carroll Posted May 5, 2015 Author Share Posted May 5, 2015 When you say a misfire, do you mean once it's fired up from the 2nd turn of the key it runs as if it's dropped a cylinder, or is it just poor warm starting? When it fired with the 'misfire' it definitely was running as though it dropped a cylinder, and sounded like a scooby. Did not really have any trouble firing up at this point (2nd turn of the key - no need to hold the throttle open), just ran lumpy. The second time around, I had to hold the throttle open to get it to fire, but then ran ok (no dropped cylinders). - - - Updated - - - Are there any fault codes stored? What is none stock about the car? I haven't checked for fault codes just yet, but no warning lights etc on the car. Will be next port of call if I don't find an easy, first time fix. Quote Link to comment Share on other sites More sharing options...
Dave Carroll Posted May 5, 2015 Author Share Posted May 5, 2015 could be a fuel pressure problem. i have had this issue with a hot start and warm restart ( on a mk3 turbo), where the fuel pressure in the fuel rail drops due to either the regulator or fuel pump one way valve and the fuel pressure drops which causes the fuel to boil so to speak in the fuel rail, and when you go to restart the engine there is only vapour in the fuel rail. toyota put on a vsv connected to the fuel pressure regulator vac/pressure pipe to vent the pipe on the regulator to increase fuel pressure (stops the regulator from seeing vac) when the engine is being started i don't know how long it's keep on for once started. to my knowledge it's only ever operated when the engine is warm/hot. i had a led connected to mine to monitor it and had only ever seen it operate once for a short time. my problem on the mk3 turbo was the fuel pressure regulator, it did not hold pressure long enough to stop the fuel from getting a vapour lock. it only ever was a problem in hot weather after a longish run. change it back to a std reg, problem sorted. i am not saying it's your regulator, because the toyota one is very good, it could be the fuel pump check valve. just something it could be? regard chris. This is an intriguing comment, as the previous owner did tell me sometimes the FPR makes a strange noise (can't say i have heard it yet). So potentially it could be as simple as a faulty FPR, especially as its non standard. The mods I currently know off that may be related to this (need to do some more digging to find anything else and exact makes/models): 1) Walbro 255lph fuel pump 2) HKS F Con piggy back ECU 3) uprated FPR (not sure on the model or make at the moment) Injectors and fuel rail are standard, from what i understand the ignition system is standard, whilst it has the usual full de-cat and Blitz Nur Spec R exhaust with HKS cam pulleys and belt. Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted May 5, 2015 Share Posted May 5, 2015 Its possible that if the FPR is a cheap aftermarket one, it could be causing trouble, I have seen this before, and as its intermittent and possibly heat related, have you checked the vacuum feed to the FPR? I have yet to have a car that actually maintains fuel pressure after a minute or two, and have never had a problem relating to this. Have you any idea what the AFRs are during the problem, I still say its could be mixture related, does it smell like its running rich? Quote Link to comment Share on other sites More sharing options...
Dave Carroll Posted May 5, 2015 Author Share Posted May 5, 2015 Its possible that if the FPR is a cheap aftermarket one, it could be causing trouble, I have seen this before, and as its intermittent and possibly heat related, have you checked the vacuum feed to the FPR? I have yet to have a car that actually maintains fuel pressure after a minute or two, and have never had a problem relating to this. Have you any idea what the AFRs are during the problem, I still say its could be mixture related, does it smell like its running rich? It does smell like it runs rich at times during idle. Also, whether or not this is related I am not sure, it idles at around 1100rpm (not missing - running smooth). No idea on the AFRs at the moment. Any recommendations on the FPR? I'd like to future proof, and seeing as the previous owner did inform me it can make 'strange noises' sometimes, it was one of the things I planned on replacing anyway. My thought is replace it with a good one and it may solve this problem too. Quote Link to comment Share on other sites More sharing options...
chrispot Posted May 5, 2015 Share Posted May 5, 2015 (edited) forgot to add if you have a leaking fuel injector this will drop the fuel pressure in the rail and can cause the fuel to boil/vapour etc. there was a member on here had hot start issues related to a injector leaking. plus one or more cylinders could/would be very rich if the fuel has not evaporated away when restarting. does your reg have a pressure gauge fitted? could one be fitted? and my mk3 turbo run very rough for a minute or so once cleared it ran fine. let us know what the problem was and if i was right about fuel pressure. regards chris Edited May 5, 2015 by chrispot (see edit history) Quote Link to comment Share on other sites More sharing options...
chrispot Posted May 5, 2015 Share Posted May 5, 2015 Its possible that if the FPR is a cheap aftermarket one, it could be causing trouble, I have seen this before, and as its intermittent and possibly heat related, have you checked the vacuum feed to the FPR? I have yet to have a car that actually maintains fuel pressure after a minute or two, and have never had a problem relating to this. Have you any idea what the AFRs are during the problem, I still say its could be mixture related, does it smell like its running rich? just out of interest what troubles have you had with cheap fuel pressure regulators? regards chris Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted May 5, 2015 Share Posted May 5, 2015 just out of interest what troubles have you had with cheap fuel pressure regulators? regards chris Basically just not maintaining a constant fuel pressure during running, It would vary the AFRs at constant load, I think its down to badly designed/manufactured valve/spring and diaphragm. Quote Link to comment Share on other sites More sharing options...
chrispot Posted May 5, 2015 Share Posted May 5, 2015 Basically just not maintaining a constant fuel pressure during running, It would vary the AFRs at constant load, I think its down to badly designed/manufactured valve/spring and diaphragm. Thanks for that, as i had brought a cheap AEM copy one a couple years ago and at the time i checked to how good copy one is, they were a bit hit and miss, but i took a chance. because of being a good dimensional copy someone replaced digraph and spring with a genuine AEM one and reported that it worked great. last question as i don't won't to block up someone elses thread. have you had any cheap FPR's that have been ok? regards chris Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted May 5, 2015 Share Posted May 5, 2015 What's wrong with using the stock one? Quote Link to comment Share on other sites More sharing options...
chrispot Posted May 5, 2015 Share Posted May 5, 2015 What's wrong with using the stock one? are you referring to me or the original poster? Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted May 5, 2015 Share Posted May 5, 2015 are you referring to me or the original poster? You, in fact 90% of people who decide an "uprated or aftermarket" fuel pressure regulator is a good idea? Quote Link to comment Share on other sites More sharing options...
chrispot Posted May 5, 2015 Share Posted May 5, 2015 (edited) there is nothing wrong with using a stock fuel pressure regulator, and the only time i would use a aftermaket fuel pressure regulator would be because i had to. my mk3 turbo came fitted with the aftermaket regulator when i brought the car. my car is still using the oem regulator. i have brought a aftermaket one for when i go single. i have brought new top feed fuel injectors and fuel rail, i could machine the rail to take the oem one but for ease of fitment when i go single i will use a aftermarket one. I would never say it's a good to change the fuel pressure regulator unless needed, as you would probably agree,what's the point. but this is not helping the original poster's problem. I would suggest to the op that he fits a OEM FPR. regards chris Edited May 5, 2015 by chrispot (see edit history) Quote Link to comment Share on other sites More sharing options...
Dave Carroll Posted May 5, 2015 Author Share Posted May 5, 2015 Thanks for the advice guys. If the advice is to go with an OEM FPR thats what I am happy to do. I do not know the reason for the aftermarket one being fitted to the car, and to be honest have never fitted an aftermarket one to any of my previous cars either, so any tips are welcome. However, before I splash the cash on an OEM one from Toyota, is there anyone who would advise going with a better aftermarket one in preparation for a fuel rail and injector kit? I don't plan on purchasing or fitting for a while yet, however, I do plan on moving the power up over the next few years and if I can future proof as I go along I am happy to do so. Thanks for the advice so far guys, and don't kill any discussion on this point on account of me, as it is all insightful and useful info for both me and anyone else who might run across this thread. Dave Quote Link to comment Share on other sites More sharing options...
chrispot Posted May 5, 2015 Share Posted May 5, 2015 Hi dave, glad we could be of some help, but do please let us know if the FPR sorts your problem, as you say could be helpful to others. regarding a FPR for future proofing i would suggest if money permits go for a branded one like AEM or Fuelab. it was cheaper for me to get top feed and FPR. but to keeps things simple you can upgrade injectors to a later date with side feed ones that way the cost of the aftermaket fpr would come off the cost buying side feed injectors, plus saving on a fuel rail, adaptors, hose and fittings etc. for now i would get a S/H oem reg Quote Link to comment Share on other sites More sharing options...
chrispot Posted May 7, 2015 Share Posted May 7, 2015 (edited) You, in fact 90% of people who decide an "uprated or aftermarket" fuel pressure regulator is a good idea? As a respected member and trader on here I thought that you would have explained as to why an aftermarket fuel pressure regulator is not a good idea? as that's what it appears that you are saying? please correct me if i am wrong. I personally think if someone wanted to fit a aftermarket regulator on their car that's their choice and there money, and if it works ok and is fitted safely what's the problem? but also if it leaks and catches fires or plays up that is also their problem? If there was some other reasoning behind your comment i would like to know, then maybe some of the 90% who have changed their regulator for a good idea? may change it back for a OEM one for the reasons that you give? regards chris Edited May 7, 2015 by chrispot added, regards chris (see edit history) Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted May 7, 2015 Share Posted May 7, 2015 As a respected tightwad it's a waste of money in most cases as the stock one is only in need of changing if it can not return enough fuel at key on, engine off, back to the tank to control desired static fuel pressure. So long as it is not a restriction in the RETURN line the stock one is just perfect. It has zero influence on how much fuel can get TO the injector rail. Many aftermarket ones are of very dubious quality and can have undesriable effects on rail pressure control. Thank you for calling me a respected member, I know I can be a bit abrasive, it comes with age and marriage! Quote Link to comment Share on other sites More sharing options...
chrispot Posted May 7, 2015 Share Posted May 7, 2015 Thank you for the answer. like you I have advised before in using an aftermarket reg to someone on this site, but for the reasons I had with my cheap fpr fitted to my old mk3 turbo. I do read a lot about cars and stuff and like to learn all the time and have read most of the posts that you have put up. and thanks to you I and others have learned something new today. please keep up the good work. regards chris. PS. I would like your input on these mods? using Hydrogen in the tyres (weight saving) running on 50% diesel ( because diesels do more mpg) fitting a magnet to fuel lines (30% more power and economy) ebay mod chip ( for another 30 bhp) inflating tyres to 120 psi ( to decrease rolling resistance) nearly forgot restrict return fuel line so more fuel gets in ( more fuel more power) of course first removing air filter so to get more air in. i am not fitting stripes, as it's not all about speed. now you can have a good moan. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted May 7, 2015 Share Posted May 7, 2015 Good mods, but you are behind the times, most Supras seem to have similar things added by the time they get to their old age Quote Link to comment Share on other sites More sharing options...
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