Hey all - we did end up going to the 2018 challenge this year (sans car) and had a great time meeting you all. Everyone was welcoming and it was really impressive to see some of those builds. Congrats the the dudes working on the parking lot build this year - it was great to watch.
Just wanted to update the thread a bit here and see if we could get some perspective or advice. We did finally get a correct ECU for the D16 motor, unfortunately it did not fix the drivability issues. Aside from a bouncing idle again (which may just be an adjustment problem) - symptoms are exactly the same:
- Uneven idle when warm, bouncing idle when cold. Car seems to want to die, then bounces back up.
- Engine seems to rev fine in neutral - but in gear - it will stutter and bog down from 2k RPM to ~4K RPM, then come back to life in the higher rev range
- Hissing sound I mostly hear from the AEM style intake that came with the car. I don't remember the sound when the D15 was in, but I could be wrong. Some threads I've read suggest this is normal, but no idea.
- Car ran fine with the D15, and the harness, distributor, sensors (Except TPS and MAP), injectors, fuel system, spark plug wires come from the working D15. We have no idea of the condition of the D16 before rebuild.
As far as the things we're considering:
- Mechanical and ignition timing are set and should be correct. We'll double check, but we are pretty sure it's on.
- TPS is from the D16 engine, not the D15 original, but it is adjusted correctly, we'll try to test this as well, and possibly swap for the D15 one.
- Injectors are from the D15 - it's possible that they are 190cc and the ECU is expecting 235cc, but supposedly the 91 HF came with 235cc injectors, we are double checking the codes
- I have an LM2 Wideband kit - is it worth throwing this on to test the fuel mix? I think it's pretty clear something is off, if using this will help me narrow down the issue somehow I'm all ears.
- Air intake is from a Z6, not the A6, and the throttle body might not be the right size or something may be off, we read this isn't a big problem, but again, not sure.
- IAC? I could see this causing the idle problems, but not sure about car under load
- We've bled the coolant, and plugs are new, we'll pull them again to check the gap
- Check for vac leak
Just wanted to put this out there to see if someone has had a similar experience and had pointers or suggestions.