CEL code 43 and 44

[91NSX#60]

Hi

I've swapped my engine this winter due to a HB failure.

Now with the new engine in (JDM unit with 42k km) I've got some issues with lugging with no to moderate acceleration (ECU in closed loop). When I presss the accelerator down, it hesitates a little second before it pulls away perfectly (ECU in open loop). Sometimes it comes up with CEL and code 43 and/or 44 wich is fwd/aft O2 sensor or fuel delivery system.
When the CEL light comes on, the engine also works fine, I suppose that is bacause it disregards certain signals from some sensors.


So far I've checked:
*fuel pressure (295 kPa)
*changed injectors (all within 2.2-2.3 Ohm)(used ones from my old engine)
*changed O2 sensors (used ones from my old engine)
*O2 sensor wiring

I have now ordered brand new O2 sensors.

Any other tips what to check?

[Kaz-kzukNA1]

Bit more extra information will help us in supporting you.


From your user name, I presume you have 91 model??

Do you know the JDM engine no.?
If so, just post the first three digits of it.
Please don’t post the full number.

For example, the engine number would look like C30A-***xxxxxxx and I only need to know the *** part.
It would be something like 100, 103, 104, 105, 106, etc.


Any extra info such as AT/MT, with/without EPS, TCS enabled/disabled, any modifications such as header, exhaust, TH body, super charger, etc may help.

[Edit:]
Forgot to ask you one important question.
Did you experience the same issue with your old engine?



Just to be clear, are you getting misfire or just the hesitation?
Are you saying that when the CEL is On, you don't get any hesitation from idle to normal driving rpm?


Your fuel pressure is slightly lower than the spec but only just.

In fact, I think you measured it with the rubber tube still connected to the pressure regulator.

If that was the case, then the data will be affected by the atoms pressure.


One quick check that you can do.

While the engine is switched off, disconnect both (front and rear) O2 sensor connectors.

Not required but to be 100% sure that there is no other failure, please reset ECU now by pulling the 7.5A Clock fuse.

This will reset all of the study co-efficient value for the fuel timer within the ECU but they won’t be used during the following test as we are going to force the ECU into Open loop mode.


Start the engine and you will immediately get CEL because there is no O2 sensors connected.


As the ECU is in the open loop mode all the time, it will use the default map which would be bit rich.

Go out for test driving session and if the engine runs fine from idle to normal driving condition, then you have one or both O2 sensor failure.


Because of the default fuel map, the fuel consumption is higher and also the pick up may not be as sharp as normal.


If your O2 sensor was the cause of issue, please remember to reset the ECU again after replacing the O2 sensors AND after completely warmed up the engine.


If this doesn’t fix the problem, then we can look into other areas but best to start with the easy bits first.

Kaz

[91NSX#60]

Thaks Kaz.

Tried to disconnect one and then the other and last both O2 sensors. With just one connected it hesitated less, and with both disconnected it works as it should. I already had 2 new sensors on order from oxygensensors.com so I hope they arrive soon.

Can O2 sensors go bad from sitting on the shelf over the winter? I tried the set from my old engine too and they did not help either. I also measured the wiring as i used the harness that came with the "new" engine, but could not find any shorts or cut/bad connection wires.

One more question for you, on the JDM engine harness, there is an extra wire spliced onto the red/yellow wire from the speed sensor to the ECU. It is spliced on about 10 inches from the ECU connector and is fitted with a round "quick disconnect" in the other end and looks pretty OEM. I only have the USDM wiring so it doesnt show there, but i guess it has something to do with the JDM 180km/h speed limiter?

Thanks,
Arve

[Kaz-kzukNA1]

Hi, Arve.

As in my post above, any additional info will help us in supporting you.


For example, as in my question, if you had the same issue with your old engine, then it could be fuel system related as well.

No idea on what kind of JDM engine you are using.... Hope it is the correct one for your ECU/MT/AT.



Based on your quick test result, you have at least getting closer to the start line of investigating the issue further.

After replacing the O2 sensor, you may still have the same issue but at least, you can eliminate one factor from the cause of your issue.


For production car O2 sensor, the contamination would be more likely to happen on how you removed it than how you stored it.

At this stage, it is not clear whether your O2 sensor is actually contaminated or not.
Both sensor to fail at the same time??? Very unlikely.....


Did you use even a tiny amount of penetrating oil when removing the sensors from your old engine by any chance?

Even a mist of oil in the air could contaminate the sensor and trigger the CEL.

You will find in my other posts that I have my own policy of not dealing with the exhaust area without having access to the spare O2 sensors.

This is based on my past experience when I triggered CEL for O2 sensor even I was extremely careful not to even splash a single drip of penetrating oil around the sensor when dealing with the exhaust pipe.


Not sure where the other set of the O2 sensors came from but if they were the ones included in your JDM engine package, then who knows what was done to them in the past.


Regarding the speed sensor wire.

Sounded like something to do with an aftermarket parts fitted (or removed) in Japan.

As far as I know, Honda doesn’t use ‘quick disconnect’ type connector or may be I didn’t understand the connector that you were referring to.

The only place that is in use is the ones inside the Bose foot well bass speaker box at the passenger floor.

There are two quick disconnect type connectors to splice/merge the cross over channels.

If it was from Japan, then very likely to be for the drive computer which has built in speed limiter canceller circuit or for the AV/SatNav system.

Kaz

[91NSX#60]

Ok, the car is a 91 MT.
The JDM engine is marked C30A-100XXXX

I did not have any issues with the old engine until the HB decided to chew into the timing belt.

The first set of O2 sensors was already installed on the oem exhaust manifolds on the new engine, I moved them over to my aftermarket headers.
The second set was from my old engine. Did not use oil neither when removing or installing them.

I might have used the wrong word describing the type of termination on the mystic second speed sensor wire. It like a bullet type terminal lug with a clear plastic insulator over it.

Thank you for your time
Arve

[Kaz-kzukNA1]

So, I can now tell that this JDM engine was built for NA1-100 VIN model in Japan until Nov/92 when NA1-120 type was introduced.


C30A-100 engine code was used for both MT and AT for early models but you can easily distinguish MT and AT engine by the diameter and design difference of the crank pulley (HB, as in your post).


The biggest difference is the cam shaft between MT and AT.

At 42K KM, it is very unlikely that this JDM engine had any TB service in the past.

TB service schedule for JDM engine is every 100K KM so I presume you don’t have any timing issue with this engine.

If worried, you can ‘T’ in to one of the four L shaped tube (I normally use #4 because that is where the manifold pressure sensor is connected) on the TH body to measure the vacuum pressure or simply remove the valve cover and check for the timing mark.


From your post, sounded like you used 2 set of O2 sensors to test the issue and all of them didn’t fix the problem…..

Very unusual but you already ordered the new set so let’s see how it goes….


Ah…. aftermarket header…..

Just a matter of interest, are you 100% sure that you have connected each O2 sensor connector to the correct port on the engine harness?

Depending on the spec of your aftermarket header, you may be using the extension cable for the Front sensor.


You could accidentally connect the Front sensor to the rear port on the engine harness and vice versa.
Not good for engine control.


Now I understood the ‘quick disconnect’ connector.


It is called as ギボシ(gi-bo-shi) in Japanese.
Again, very common for aftermarket parts usage.


Kaz

[91NSX#60]

I changed the timing belt and water pump before I put the new engine in. Also plugs, plug seals and cam cover gasket. Checked and double checked the timing and marks several times as I did not need two engines with bent valves

I'm pretty sure the connectors for the O2 sensors are connected correctly.
I dont quite understand how it can be anything else than the O2 sensors when the engine works perfectly with them disconnected. Only thing I can think of is if the ECU disregards other signals when the CEL comes on with the codes for the O2 sensors?

[91NSX#60]

Both O2 sensors replaced yesterday, car is running like a dream again No CEL, no hesitation.