In the morning when i start the car it runs very aggressive. Once you drive the car 10 km the car starts strange behavior. Once car is hot it would Idle Low (500), low pickup, hesitation........

Setup:
Car is 92 accord
F18B VTEC
F23A VTEC ECU
92 accord original auto transmission
CNG installed few years ago

Tests and Experiments:
Throttle Body Tuning + EGR+FITV+IAVC cleaning already done
Tappet tightening done
Battery Voltage while Running 13.6
Voltage at alternator when I touch its body and Positive (connected with battery wire) is 14.1 V
Primary O2 Sensor was disabled when I purchased the car
Cant Find Secondary O2
Radiator and AC Fans are Direct


Important: The car is on CNG. The thing with CNG is it over rides the MAP Sensor.Takes Input from TPS and sends signal accordingly to MAP. The CNG Venturi is added between air cleaner pipe and throttle body.

If car is on CNG the Injectors are turned of by its CNG Emulator and timing gets advanced. Its normal many cars have CNG installed.

Once you are on CNG ECU can not control the fuel Mixture or Injectors so o2 sensors can be ruled out.

I suspect two things
First is Alternator wiring because there should be same voltage at alternator and battery here they are different and My alternator gets too hot. Its original non repaired,

Second thing may the the Hydraulic Transmission as the F18B came with CVT transmission i guess so its connectors are not connector and ECU might be in Limp Mode

Please guide me the debugging path

 

i gotta be honest...i would swap that engine out with a jdm f22a and go back to stock or atleast go h22a

you're currently using an engine with an ecu that don't match up

 

Problem is this car got registered with F18B even it is not orignal. If i swap any other engine this car would become a non market car and no one would dare to buy should i change the ECU ? i suppose wiring would all be the same......

 

If you purchased the engine from an importer, see if they can get you the correct engine harness and ECU for the F18B. F23A is half a litre larger and for us here in U.S.A. were in '98-'02 Accord OBDII cars.
I have no idea what parts you have. I would think if you cannot locate a F18B ECU that the next closest thing would be a F22B1 ECU
Disabled as in it was never there, someone just never connected it, or someone cut the leads to the O2 sensor?
I know in some markets due to fuel availability, often leaded only being available, that the O2 circuit is not used since it would be not possible with leaded gas.
Secondary O2 sensors were only used on OBDII vehicles, here in the USA that was on '96 and newer model years. In the EU OBDII wasnt until '01.

You are going to have to let us know a few things.
1. What country are you in? This is mostly a U.S.A. board with U.S. members.
2. What domestic market is the car originally for? JDM, EDM, USDM, etc
3. Where are you procuring your parts, what year of car(s) and what market?

Well this will be harder to help you in diagnosing.
MAP(manifold absolute pressure) sensor monitors how much pressure is in the intake manifold. This is usually negative pressure/vacuum
TPS(throttle position sensor/switch) is how the ECU knows what throttle angle the throttle body blade is.

Why would the CNG system override the MAP sensor readings?
Is there a secondary or piggy back ECU that works with the cars original ECU?
If you are using an F23A1 ECU then it is most likely OBDII based. And the Honda OBDII computers from '96-'~02 are not easy to tune, nor is the OBDII programming going to be easily 'fooled' by 'tricks' that work on older models.
Again if you are using an OBDII ECU it will not be easy to fool. It is a far more powerful and sophisticated ECU than earlier F18/20/22 units.
As for 'ruling out' O2 sensors. If the ECU is looking for feedback from the O2 during closed loop operation. If it does not 'see' the O2 sensor it will set a code and go into a limp mode which will greatly affect general performance.
Is this orginal to the '92 Accord or the the F18B engine?
CVT in a '92 Accord?
AFAIK Honda did not have CVT until '96 and even then it was used in Civics and some micro cars.
Or did this transmission come with the F18B engine?

We need more information on where you are, where you are getting your parts from(donor vehicles, year, model, sub model), and who makes this CNG system.

This is mostly a U.S. members board, so when you say F18 most are going to think of this...


not this...

 

Thank you for such a detailed reply.

1. I suppose that this is original Engine Harness because there is no alteration in wiring harness. its in original Packing. its ODBIIb wiring.
2. I Live in Pakistan and this engine came here in 98-2000 Accord also known as CF-3 (i suppose 94 accord may have the same but above 1.8 are very rare)
3. The Sensor wire as in your pic was cut. The swap guys did not bothered to install it.
4. The car is JDM.
5. We get parts from junk yard. There are many shops who sell engines, suspensions, body parts and even half cut cars. Even i saw lexus V8 engines there just for 500 USD and F23A is 800USD with wiring and tranny
6. Well do not know but MAP Signal wire goes to mini controller (basically relay box) and from that controller to the MAP Ecu Input Pin.You can understand from here http://www.pakwheels.com/blog/2011/1...anceremulator/
7. Its not Piggyback ECU its just a relay box with many relays. If car is on Petrol the Emulator would allow ECU to fire Injectors otherwise not there are six relays four for injectors and other for MAP and Oxygen Sensors i guess.
8.Alternator is F18B engine's Alternator
9. No the default 92 tranny is not CVT i know but friend told me that the transmission that came with F18B engine is CVT or also known as electronic transmission. The current transmission is default one that came in 92. Mechanics did not bother to swap transmission when engine was swapped.

Following are the pictures of my Transmission.