I've been tracking down some idle issues and I noticed while checking that I have (with key to ON):

8V at one secondary injector connector.

~1V at other secondary injector connector

~6V at the leading coils.

As far as I know these should all be 12V with key to ON. I didn't check the primaries because they're hard to reach, but based on my crappy idle I'm guessing they're suffering from similar issues.

I know my grounds are good, I've checked all of them. I have a spare ECU I can pop in to check if there's a difference, but I know for a fact this second ECU did not help with the idle issue.

Which leads to my question: Where do I even start trying to diagnose this? I'd normally suspect a bad ECU but since my second ECU is behaving similarly I doubt that's it. Unless I happen to have two identically bad ECUs.

I'm done for the night but tomorrow I'll swap ECUs and measure the voltages again just in case. Any suggestions for where I can start diagnosing this would be appreciated.

 

So I tested again this morning and found that the connectors I mentioned above DO have 12V when I put the other multimeter probe on a body ground, but not through its connector. So I was probably just reading them wrong last night.

Another weird thing though, when setting timing (750rpm, initial set connector is jumped) my leading and trailing coils are firing at the same time. Both are firing at the leading mark. Not sure what could cause this, but I don't have crossfire as far as I can tell and I have tried different plug wires.

 

So I've done some more testing and here are my results:

L1, L2, T1 fire at exactly the same time (corresponding to the leading mark on the pulley).

T2 fires completely unrelated (presumably 180° off but I of course can't verify this because there's no mark there).

Now L1 and L2 firing at the same time makes sense, as they are a wasted spark system, but AFAIK T1 should be firing at the second (trailing) mark on the pulley. As it is my car is currently running zero split.

I tried separating the plug wires and was very careful with the timing light so as to only pick up the desired leads. No change.

One other thing I'm noticing is that when I press the throttle linkage down while watching the pulley with a light on the L1 lead, the timing retards toward and then past the trailing mark before springing back to the advanced side. I would expect it to smoothly advance.

I'm on a completely stock ECU, so I'm not sure what can be causing this. Zero split, ignition retarding briefly on acceleration before advancing like normal. And this would explain the slight bog I've had getting onto throttle since I've owned the car.

I'm a bit stumped as to where I should even begin to search.

 

Tps?

 

TPS is good, set properly. I set it with the light method, but just confirmed with voltage method and it's good.

 

Alright, so one mystery is solved. I dug into the training manuals today and found out the ECU locks leading and trailing timing together at idle when the AC is on. My AC is not currently installed, but on a hunch I checked voltage at pin 1E on the ECU and found it to be almost zero (should be 12V with AC off). I imagine a switch someplace has failed in the "AC is running" position.

Ran a temporary jumper and wouldn't you know it, my CAS now lines up in the right place and the timing split is normal. Advance works as it should.

Now my idle is still crap, but at least I don't have to worry about the timing. Going to backprobe the rest of the ECU pins and check everything thoroughly and see if anything else is out of spec.

 

sweet. i've been using a safety pin to probe the ECU pins, it has the pin to do the probing and then the multi meter lead will go into the safety part and lock in there, so its pretty handy

 

Here's the info for ECU testing in case someone needs it in the future, plus the relevant section from the training manual.







Thanks j9fd3s for the safety-pin trick, it makes this a lot simpler. Oh, and anyone doing similar testing should keep in mind that the pinout above is from the side facing the ECU. This makes sense when the ECU is plugged in but is less intuitive if you're trying to trace the wires back to someplace else or verify the grounds.