Fixing the many problems I had with my JZA70 ECU

The problem

OK, the first problem I had was quite a significant one. The car would run fine for a while and then out of the blue it would just feel as if it was running on 4 out of 6. It would blow smoke out of the rear. No ECU warning light would come on. If I started the car from cold in this state it would blow horrendous clouds of white smoke out of the rear and wouldnt run very well at all. If you took a whiff of the exhaust if smelt like there was a couple of litres of petrol in the exhaust.

After a severe amount of diagnostics, using an oscilloscope to view the injector pulse signals, it could be seen that two of the injectors were being held permanently open. Presumably just blowing unburnt fuel right through two of the cylinders.

For two of the injectors to be held open, it either had to be a wiring fault between the ECU and the injectors, or a fault in the ECU itself. I ruled out the wiring with several checks, so it had to be the ECU.

The solution

I head read articles elsewhere on the web that some of the capacitors inside the ECU are prone to bursting and causing random problems on these cars.

With nothing to lose, lets have a look inside the ECU. Here it is dismantled and split into two.

Inspection of all of the ectroclytic capacitors showed significant leakage, to the point where they were starting to corrode the main CPU board.

You can see from the image above, that the capacitor has leaked onto the board and is starting to damage the electrical tracks. This is almost at the point of being too damaged for my skills to repair. I deceided to replace every electrolytic capacitor, even if they looked broken or not. After marking them all up and ordering spares, I removed them and cleaned up the PCB the best I could.

If you look at this particular area up against a light, you can see that there has been track damage due to the corrosive effect of the inside of the capacitor leaking onto the PCB. This can be seen just above the negative symbol to the left of where the capacitor is seated.

To fix this I will need to lay a track bypass using a piece of hookup wire. You can trace back to where the other end of the wire can be attached using a multimeter and visual inspection.

Making sure the right capacitors go in the right places, and that they are all in the right way round, everything was soldered back in place and refitted.