corollakid Posted July 11, 2022 Report Share Posted July 11, 2022 Hi Guys and Gals, I was speaking to an auto electrician the other day and he was telling me about ECU problems with late 80's early 90'S Toyotas. He has 2 late 80's 20valve Corollas and was having trouble with one of them, namely starting again after a run. Apparently Toyota fitted some inferior capacitors in various models his being one and MR2's as well and this affected American versions and import cars also. Other problems were rough running, alarm problems, poor starting etc. I can't remember the name of the capacitors but they were brown in colour. So has any one in the club had similar problems and found them extremely difficult to solve, if so it might be worth while removing the top of the ECU and checking if the said capacitors are leaking and replacements are fairly cheap and could stop the vehicle being scrapped. Other ECU's in the vehicle could also be affected. Not sure if Celica's were affected so it will be interesting to find out if any member has had similar problems. Regards Stu. Link to comment Share on other sites More sharing options...
Xanadu Posted July 11, 2022 Report Share Posted July 11, 2022 7 minutes ago, corollakid said: So has any one in the club had similar problems... It is already a known problem with the 5th Generation GT-Four, but I think this is mainly due to the age of these cars. Remember, these capacitors have been faithfully doing their job for 25-30 years without any issues, so they were bound to die sometime. Chris will probably be adding a reply shortly, so stay tuned! Link to comment Share on other sites More sharing options...
_Chris_ Posted July 13, 2022 Report Share Posted July 13, 2022 http://www.gt4dc.co.uk/forum/viewtopic.php?f=2&t=5617 A good few years on now and while it's been mostly gt4's it's also affected other models and the gen 6's as well. I suspect it's more apparent in the rarest models where spares aren't readily available so people ask fot help. My opinion is that it isn't poor quality capacitors although that is a possibility. We're also starting to get some of the other values failing now. I suspect it's probably a combination of age, temperature and use. Heat is one of the primary causes of ageing, and the ECU is mounted under the heater outlet on top of the exhaust tunnel !! The other ageing factor is high frequency / high ripple current, and the first capacitors to fail were on the power rail feeding the idle solenoid. I did switch to ceramic capacitors for replacement of the 10uF as these don't suffer the above problems and are more suited to 'decoupling' on supply rails, however someone reported having a problem with the ecu, changed back to electrolytics and it was fine. Link to comment Share on other sites More sharing options...
bazz54 Posted July 19, 2022 Report Share Posted July 19, 2022 (edited) I mess around with vintage radios/electronics and the sort of electrolytic capacitors shown in the picture above do often degrade, even in household electronics. It shows up most in low value components (10uF and less). High temperatures will certainly accelerate the problem. As for ceramics, I didn't know you could get ceramics with values of 10uF; I think the largest value of ceramic I've ever seen would be 0.1uF. The quality of electrolytics has improved enormously over the last 20-30years, but the difference in quality between no-name components and the big-name components can be huge. There's a parameter called "effective series resistance" (ESR) and good quality modern caps have appreciably better ESR than old components and cheap components. Build quality and life expectancy is also much better in quality brands. Obviously, the quality brands are appreciable more expensive to buy. Edited July 19, 2022 by bazz54 Link to comment Share on other sites More sharing options...
slybunda Posted July 20, 2022 Report Share Posted July 20, 2022 Common on old motherboards. Badcaps.net has details. Would be good if someone could put together a shopping list of caps needed for ecu of various celica generations. Link to comment Share on other sites More sharing options...
bazz54 Posted July 21, 2022 Report Share Posted July 21, 2022 (edited) 15 hours ago, slybunda said: Would be good if someone could put together a shopping list of caps needed for ecu of various celica generations. Could some tell me, to make a list of caps for a particular ECU, are there any Toyota sources (service sheets?) available or is it a case of taking an ECU, taking the lid off and spotting the (electrolytic) caps? I've not heard of this problem arising with Gen7's yet (?), but I'd be willing to get involved in compiling a Gen7 list. A quick look on Google suggests that there's a lot of info already there about cap replacement in ECU's in general. Edited July 21, 2022 by bazz54 Link to comment Share on other sites More sharing options...
_Chris_ Posted July 21, 2022 Report Share Posted July 21, 2022 On 19/07/2022 at 05:05, bazz54 said: I mess around with vintage radios/electronics and the sort of electrolytic capacitors shown in the picture above do often degrade, even in household electronics. It shows up most in low value components (10uF and less). High temperatures will certainly accelerate the problem. As for ceramics, I didn't know you could get ceramics with values of 10uF; I think the largest value of ceramic I've ever seen would be 0.1uF. The quality of electrolytics has improved enormously over the last 20-30years, but the difference in quality between no-name components and the big-name components can be huge. There's a parameter called "effective series resistance" (ESR) and good quality modern caps have appreciably better ESR than old components and cheap components. Build quality and life expectancy is also much better in quality brands. Obviously, the quality brands are appreciable more expensive to buy. When these ecu's were designed, 10uF ceramics were unhears of. I think 0.47 was about the limit.The surface mount era has brought about minaturisation of all components. You can now get 10uF in 0402 size (1mm x 1/2mm) although not up to 16V. This has also impacted on through hole versions. ESR is part and parcel of why electrolytics don't like ripple, particularly high freqency ripple. Where the larger capacity of an electrolytic is needed, it is normal to put a ceramic capacitor in paralell to handle the high frequency / sharp edges of any ripple. This wasn't done on the capacitors I've looked at in the ECU. Electrolytics are much less common in modern designs, mainly because they don't apply well to surface mount for 2 reasons. Firstly the larger sizes would just break off the board with any vibration or shock. Secondly, surface mount soldering is done in an oven which heats the component as well as the board up to soldering temperature. Although through hole electrolytics can be used, it's very difficult to automate the through hole assembly so it;s not ecconomic for mass market. Link to comment Share on other sites More sharing options...
slybunda Posted July 22, 2022 Report Share Posted July 22, 2022 Would replacing with polymer caps be an upgrade? Link to comment Share on other sites More sharing options...
_Chris_ Posted July 22, 2022 Report Share Posted July 22, 2022 Polymer capacitors are fairly new and I don't have much experience. I tend to use Tantalum for the medium capacity / low ESR applications. For the higher capacity / higher voltage stuff where Tantalum isn't available, neither is polymer so I stick with the traditional electrolytic plus paralell ceramic or polyester. Nowadays for a 10uF / 12V decoupling application like the main caps that fail in the ECU I would just use ceramic, although Polymer may cope with over-voltage surges better. Link to comment Share on other sites More sharing options...
bazz54 Posted July 22, 2022 Report Share Posted July 22, 2022 I've stayed away from anything using SMD's; would need a younger pair of eyes to cope with those. As for tantalum, I've always regarded those as components that need very carefully designed circuits to be reliable. I have an old scope made by a Japanese company called Leader (not sure if they are still around) and that used to blow tants (which were the original fitments) and I got fed up with them, put in good quality aluminium electrolytics and never looked back. The practice of putting small ceramics alongside electrolytics is common practice in ham a radio equipment where there may be some level of RF around. The picture above shows traditional through-hole components in the Gen 5 ECU; have you ever taken a look to see what a Gen7 ECU looks like inside? Link to comment Share on other sites More sharing options...
_Chris_ Posted July 23, 2022 Report Share Posted July 23, 2022 Not looked in a gen 7. The gen 6 has quite a few SMT but still quite a bit of through hole. To a certain extent I was forced into SMT as many of the newer chips just aren't made in through hole. I'm fortunate to have a local SMT production company which does small quantities without huge charges so it's actually become cheaper than through hole even in 25's. I am starting to be able to handle SMT myself although only for prototypes, not for production as I don't have an oven to ensure the correct heating profile to solder reliably under chips whithout overheating them. These things help enourmously: https://uk.rs-online.com/web/p/magnifiers/1830966 Tantalums are fine provided you stay within the voltage ratings, they are very intolerant of voltage surges. Although they are low ESR I still tend to use them with a paralell ceramic, this may also make a difference. Link to comment Share on other sites More sharing options...
slybunda Posted January 6, 2023 Report Share Posted January 6, 2023 anyone taken the lid of a gen7 ecu and got a photo of the board inside? Link to comment Share on other sites More sharing options...
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