940 & 960 LH2.4 954 ECU running rough/rich
This is kind of a follow-on from this thread where I asked about the chip that was in an 954 ECU that I was yet to test. I've since got the car up and running, and that ECU runs poorly and I'm trying to figure out why.
As of right now, I have two LH2.4 ECUs.
- A green-label 563 ECU out of a '91 940 Turbo that was running when removed. Working well in idle, cruise and boost.
- A white-label 954 ECU that came with the car, unknown condition. Barely idles, dies and runs mega rich (~10AFR at idle).
I have a feeling that the 954 ECU is just a dud, because regardless of the fuel chip, it doesn't appear to run correctly. I don't know the history on it. I've been running the 563 ECU on the car for about 1000KM now with zero issues, but I got some chips to swap into the 9xx ECU and would prefer to run as late an ECU where possible.
I haven't fully stripped it down to inspect it to see if there's any blown components but the few electrolytic caps I can see appear to be ok.
- Running a Spartan 2 wideband O2 sensor with simulated narrowband output feeding back to LH2.4. Works perfectly with 563 ECU. Have run with the O2 sensor disconnected to disable narrowband output and made no difference.
- Running either the original 954 chip (see other thread linked) or aftermarket chip both give the same rough and rich idle.
- Can't pull any diagnostic codes or seem to reset codes. When attempting to reset on position 2, sometimes it won't respond, and sometimes after ~5 seconds the LED will come on again.
Startup and idle on both ECUs:
- Video of startup and rough idle
- Video of attempting to pull/reset codes and then the light stays on?
- Video of doing the same, then running afterwards, no difference
- After running the 954 so runs rougher than it normally would at start) but then idling no worries after that:
Is it possible there's something I'm missing? With exactly the same setup, the two ECUs should behave the same, right? I can't figure out why it runs so poorly on the 954 ECU and works perfectly on the 563.
If you've got a LH2.4 turbo ECU that you have and might wish to sell to me, PM me please! Also got thread here. 😀