Yeah, yeah, always something new to learn hehe. Enjoy the gloat! :-P

On 18/09/2013 7:02 AM, "Suzy W" <> wrote:
1jz ecus are very well known for crapping themselves :D

*gloat gloat* yw :)

On Wed, Sep 18, 2013 at 6:42 PM, Dennis de Jong <> wrote:
Hi all,

I have a question regarding the idle on a 1jz-gte. First a little bit of background which might be helpful to others with weird electrical issues.

I discovered some strange electrical problems which involved the catalytic converter light flickering on and off while the car was running and turning off whenever I pressed the brake pedal. It turned out pressing the brake pedal increased the voltage at the CCO pinout on the ECU, this pushed the voltage above what was needed to switch the light on (low voltage means an overheating catalytic converter). I thought this was odd since I don't have a catalytic converter or a sensor. Furthermore, pressing on the brake pedal also increased the idle speed by ~100rpm. It only did this when the brake light circuit was intact, so it was not a vacuum issue.

Lots of reading on the interweb yielded little help, apart from general confusion regarding the CCO circuit and whether or not removing the sensor made a difference to  fuel/air mixture. I can't say for sure whether the ECU uses this value for any engine management, even with the manual! But when there is no sensor, the ECU defaults to approximately 3 volts, which is in the middle of the normal voltage range for the catalytic converter (2.5 to 5.5 volts). Essentially the ECU only seems to care whether the voltage in the CCO circuit is above approximately 2 volts as far as I can tell.

After a lot of fiddling about testing the loom and learning a lot along the way, a friend of mine who does a lot of work with electronics talked me through the circuit and a bit about ECU operation. This led to investigating the ECU which, 7M owners feel free to gloat here, had leaking capacitors, these had been fixed before by someone else, but were leaking again, I'm not sure why this was as the ECU was not the one that came with the front cut.

Replacing these solved the above problems and some others which were more subtle. The idle now stays at normal speed ~750rpm when the car is warmed up, but  still sounds quite "messy". I haven't heard many 1jz's idle, and can't seem to find any on youtube that haven't been modified. Only modifications for my car are the muffler, pod filter and aftermarket blow off valve (came with the front cut from Japan). I've uploaded a video of my car idling to (easier to hear with head phones):

Just wondering if this is normal idle for an unmodified 1JZ? The reason I'm asking is that I want to make sure:

A) I'm not trying to create a problem when there is none.
B) Whether there's not another issue I need to attend to while I'm tinkering
C) Whether there's a possibility some other gremlin in the ISC system caused the capacitors to start leaking.

Any thoughts would be much appreciated.
Supra Club of New Zealand -
Website sponsored by Alltech Diesel & Turbocharger


7M POWAH! ;)
Supra Club of New Zealand -
Website sponsored by Alltech Diesel & Turbocharger