Before I present my problem here is some background info:

Vehicle: 1997 Accord
Previous Engine: F22B DOHC
ECU: P0J (OBD2)


Swapped Engine: H23 VTEC
ECU: P91 - Chromed Tuned. O2 sensors was deleted

Significant modification after the swap: removed catalytic converter and O2 sensors.


Experience after the swap:
1st month the engine was strong, noticeable powerful than the F22B as expected. However in the 2nd month I notice power decline, it drives like the F22B. 3rd month, there was noticeable misfire and backfires. The misfires become more and black smoke become apparent and the engine suddenly would not start.

I checked the spark plugs, all of it are powder black (there is no oil on them), sign of very rich mix.

I changed the plugs with new ones, the misfires were still horrible. I kept the engine running in less than 10 minutes, then took off the plugs and again all of them are black.

things I have done:
change NEW MAP sensor
change NEW distributor (full set), New Ignition wires and again New spark plugs
Clean the IACV

run the engine and again in less than 10 or 5 mins, all plugs are black.. engine misfires a lot and smoke are very black

What I did just this morning:
Change the ECU with my old OBD2 ECU, and clean the spark plugs from the black powder. When I run the engine it was alot better than before, though light black smoke still comes out from the exhaust. I am not expecting anything much from this, just for the sake of testing the ECUs.

My questions:
1. Does it mean that my Tuned ECU (P91) was bad?
2. Do I need to send the car for re-tune or I need to change my ECU with a P28 and retune?
3. Does this anything to do with the catalytic converter and O2 sensor removed, in spite it was removed in the ECU tune?
4. Are there other possible factors? I already removed the possibility of injectors as all the plugs are affected at one time.


sorry for a long story, but i believe more info will help you help me. I really need your advice. Thanks a lot.

 

number 1 reason for running rich is an exhaust leak I would start there

 

In 20+ years of Honda repair I've Never seen a bad MAP Sensor and with your test using the old ECM, I'd say that it's a good bet the new one failed. Remove the cover and see if it smells burnt. Also look for a black spot on the circuit board or a burnt component. Usually not too hard to tell when an ECM gets toasted.

 

I've opened the ECM before I read your post. I did not smell anything burnt, but I'll take a closer look for any burnt component.

 

I just realized you have no oxygen sensors. I'm no tuner guru but it's a safe bet you need oxygen sensors unless you're always at wide open throttle such as during racing conditions.

 

But when the ECM was tuned, the O2 sensors was disabled. To my understanding it will not be considered anymore when ECM does the A/F mix.

 

The only time i heard of oxygen sensors being disabled is on a car that is race only. Again, I'm not tuner guru but this is just what I have noticed, myself.

 

I got the issues. The ECM was burned on the PCV near where you plug the wire harness. Thank you guys!