Hello once again , I am at an awe at the moment.
So I will recap from the start real quick.
I have a 96-98 EJ9 (European EK) , it came with a D14A4 engine and SFi
Swapped a B16A2 with OBD2B harness and convert everything essentially to OBD2B , used the stock ecu P2T. worked fine , the ecu is having some internal issues , changed few stuff but the problem persists.
Done some upgrades to the engine (higher CR and bigger exhaust 55mm)

Used an OBD2B to OBD1 adapter and used a known working ecu(P30) with hondata.
Today I installed my wideband (AEM X series) and all is fine , can get to tuning.
But I also changed the Distributor.
The stock one was a TD-81U , (still have it , but needs a complete rebuild)
I bought a replacement one. Part numberH955-81 , its essentially a TD-81U (direct swap) its from Ashuki / Blue Print.
The car works amazing. mechanically speaking its awesome. no problems vtec kicks in good and hard , etc.
The problem is with my tacho. After few kms it started flicking even on idle (without changing nothing , nor the AFRs or the behavior of the engine) Its only affecting the tachometer.

As soon as I turn my headlights on , the tacho shuts off , like when you have the engine shut. (does not move at all.)
Swapped the ECU back to the P2T and the tacho was stable , no issues with the headlights , worked flawlessly.
Swapped back the P30 , was working fine and no issues with the headlights and when we pushed , 1-2 vtec , it started doing it again.

I can't understand what is happening , (nothing else changed in the car) , also I removed the wideband , did nothing , did not affect it at all.

Basically swapped the distributor , but its works with P2T and with P30 , only when pushed and afterwards its just messing around.

Has anyone had an similar problems before?

 

I think I need to do the NEP signal , just not sure why it did work before..

 

Your problem is likely the ICM inside the replacement distributor... the output signal for the tach signal is weak. If you are not getting sensor codes from the OE distributor, I would swap out the coil and try it again and ditch the aftermarket dizzy.

 

Oh , I see. but why with the P2T would work? is it because the signal is going through the ecu?

 

The P2T would output a tach signal on the NEP wire, and a parallel identical signal on the ICM output. NEP runs to the tach, and the ICM controls when the distributor fires spark.

The P30 only outputs a tach/ICM signal on the ICM wire. You can split the ICM to run into the NEP wire as well, giving the tach the signal it needs to work. I've done that on mulitple cars without issues. The alternative is to run a wire from the distributor's tach output to the NEP pin on the harness.

Between your P2T and your P30 swapping you have an adapter harness, no? Double check the splice between the ICM pin and the NEP pin is solid. If you have the tach signal wired from the distributor, try switching it to the ICM on the P30, or visa versa.

 

Thank you for your input , I appreciate it , can you point me which pins should I look at?
I see that in the OBD2B should be the A19 , from a search I did I think in the p30 should be the B15 but not sure.