1JZ ECU leaking capacitors.

[Slim]

I was talking to my mechanic yesterday and mentioned the 1JZ ECU's tended to die due to leaking capacitors fucking things up.

He suggested it's not necessarily the fault of the capacitors, rather it was due to some other part of the ECU (idle speed circuit or something) ageing/malfunctioning and thus sending too much current through the capacitors. The capacitors can't handle it and blow up.

He said that it was most common on Nissans whereby this happens and the excessive current makes the capacitors get hot, blow up like ballons and then go pop spilling their guts over the PCB.

Does this sound like a feasible theory? I've often wondered why the capacitors died/leaked when things like Televisions and amplifiers have more capacitors in them but can happily function for decades without issues. Is it really the capacitors fault or something else that dies which in turn kills them?

The reason i ask is because maybe people are fixing the symptom rather than the problem when they replace blown capacitors and thus is only a temporary solution.

[Darrien]

10 characters!

[Darrien]

Some companies decided to steal an electrolyte formula from another competitor. Little be known to them, the stolen formula was incomplete and flawed. They didn't discover this until it was too late and they had manufactured and distributed literally MILLIONS of these flawed capacitors. It was way too late for any kind of recall, and even today, these crappy components are being used in new boards. As I mentioned before, I believe this problem runs much deeper than simply an industrial espionage screw-up, as that incident was exposed years ago, and the problem still exists today. Nowadays, it just boils down to corporate bean counters cutting corners to save money by using shoddy components.

.........


In more technical terms, this is is what actually happens to the capacitor...in the simplest of terms. Think of an electrolytic capacitors as a battery. They are designed to store a charge and release that charge depending on the specific requirements of the circuit. Inside the capacitor there are two metal plates with dielectric material between them, wrapped in paper, filled with acid (electrolyte), and sealed in its housing or 'canister'. What happens is the flawed electrolyte prematurely deteriorates and dries up. When this happens the capacitance value changes, becomes erratic, and can even short completely, which obviously causes the circuit to malfunction. On your motherboard, this results in system instabilities or complete failure of your board.

Sound convincing to me!

[JP]

If you trace out the leaking caps in a 1J ECU they're on more than one circuit.

I've seen leaking caps in 1J and AE101 20V ECU's, the 20V's usually have the caps associated with the ISCV go, but the 1J's usually have the caps associated with the o2 sensor, ignition and ISCV go, in addition to the cap at the main 12V input.

www.badcaps.net has a fair amount of info on leaking caps, but IMHO the 1J's etc are failing due to age more than anything else, they are usually at least 15 years old.

[chris davey]

Another great reason to get an aftermarket ecu

[NeoNasty]

Remove them and replace with better quality caps before more damage is done.

Many amps and Tvs have leaking caps. Its not restricted to 1J ecus at all. Many of the older Lexus cd stackers. Celsior, Soarer, etc etc have badly leaking caps on their RF boards.

Electrolitic caps are well knows for leakng after years. Sometimes boards need to be replaced, sometimes you just clean up the board and replace the cat piss caps.

Luck of the draw.

[richzx]

But do the caps have to be replaced with ones of the same rating? Can slightly higher rated caps be used, as I see a lot of guys using 2 in unison as opposed to 1 lightly higher rated one. I know the ones for 1J ecu's are hard to find. BTW I have no idea what I am talking about so don't ask me any technical questions! I'm too scared to open my ecu and look!
Rich

[hamgatan]

JP weren't you experimenting with the use of caps from 7M ECU's on the 1J? How did that go?

[JP]

On the first one I did I had trouble sourcing a 15uF cap, so stole a good one out of an MX83 7mge ECU.

Since then I've been able to source all the right caps from http://au.farnell.com/

[richzx]

Is there an issue using say a 20uF cap though? I will use the right ones if I can get them but out of curiosity is using a 20uF in place of a 15uF a problem? Should I replace mine even if they aren't leaking?

[JP]

I've been told it's ok to use a higher voltage cap, not sure about the capacitance though, been too long since I did that at uni.

I'd replace them proactively, I've done six JZX81/JZA70 ECU's now, and every one had at least two caps that were leaking or starting to leak. Some you couldn't see properly until the cap is desoldered.

[broken22]

Is there an issue using say a 20uF cap though? I will use the right ones if I can get them but out of curiosity is using a 20uF in place of a 15uF a problem? Should I replace mine even if they aren't leaking?

Voltage rating can be higher. A lot of TV power supplies fail due to caps being fitted running at or very near their voltage rating. Higher voltage rated caps cost more, its all about keeping the production costs down.

I would not substitute a different capacitor value. If you get stuck you can combine smaller value capacitors in PARALLEL to get the required value.

[camrygt?]

Caps mainly fail due to heat as mentioned above they dry out or leak, if the voltage applied to the cap is close to its rating they tend to run hotter..ie shorter life.

you can subsitute higher voltage ratings no problems (better if you can physically fit the highter voltage rating it will normally last longer than one running very close to its rating)

you can't really change the uf value without knowing how the circuit really works, try to keep these close to orginal
If you need a 15 uf use a 10uf and a 4.7uf in parrallel ie + pin to + pin and - pin to - pin that will give you 14.7uf which is close enough (they are fairly inaccurate in the rating to start with up to about 10%)

Jaycar quote capacitor life as about 1000hours at the rated temperature (1J ecus use 85 degree caps, jaycar sell 105 degree caps.. jaycar ones will/should last much longer at higher temps than the stock 1j ones

you can also wire caps in series ie +capacitor1- joins to +capacitor2- the voltage rating then doubles and the uf value is halved (the 2 values must be the same for this to be true) ie two 100uf 25v caps in series will give you a single 50uf and 50V

[broken22]

yes joining capacitors together uses the same formulas as resistors, but vice versa for series/parallel. If that makes sense.

Any easy way to tell if an electrolytic capacitor is sus, is to look at the top of the can. It should be flat, if it has started to swell I would change it.

[rob_o]

yes joining capacitors together uses the same formulas as resistors, but vice versa for series/parallel. If that makes sense.

Any easy way to tell if an electrolytic capacitor is sus, is to look at the top of the can. It should be flat, if it has started to swell I would change it.

One of mine has started leaking out of the bottom even though the top is still flat.