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Today at Atelier Kaz - Private NSX Enthusiast, ex-Honda R&D engineer with F1, Indy/CART background

Intermittent Engine (or something else) Issue 01

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So, as reported earlier, another owner visited my place to have his engine diagnosed.

It was checked by Honda with no faults found and very likely to be the case that they couldn’t re-create the same issue.
I was told that the IG coil, spark plug, O2 sensors and possibly the Fuel Pressure, etc were checked by them with no fault found.
Also being told that the battery was healthy, the main relay was replaced, etc.


The NSX is full OBD-II spec AT model.


So, started with the Q&A session as usual and based on what I heard, it seemed that there were three issues.


  • On one occasion, Engine Check Light (ECL) or something in amber/yellow at the left top corner of the dash started to blink at very-very fast rate. Engine felt very sluggish/heavy/slow below about 40mph. No error code stored. Stopped the engine, re-started, no more ECL and the engine kept running fine.


  • One another occasion, ECL started to blink again but this time, it was about at 1Hz (serious engine issue that may cause CAT failure). Engine was very sluggish below about 40mph. No error code stored. Stopped the engine, re-sarted, no more ECL and the engine kept running fine.


  • It seemed that this sluggish behaviour started to happen after replacing the OEM manifold to the aftermarket header. During and shortly after the header installation, three of the four O2 sensors were replaced by the header installer as well as by Honda. Even with these sensors, the car still feels very slow below about 40mph but happy above that speed range. Due to the slow traffic around the place where the owner lives, he continuously has to press quite hard on the TH pedal to keep up even with the slow traffic.


  • The owner has never tried to use F-matic to manually shift down to raise the engine rpm while driving below 40mph to see whether it makes any changes or not.


So, with the limited time available, I asked the owner to carry out base running without touching anything while I was in the passenger seat.

Then, got back to my place, disconnected the Front Primary O2 sensor to force the system into Open Loop mode and asked the owner to drive the same route in similar manner.

Unfortunately, there was not much difference and both of us agreed that it was marginally better but not much and still slow below 40mph.

I didn’t drive the car as it was too dark so will see how it goes from tomorrow.

I just hope, the issues can be re-created within this week while the car is here…


Kaz
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Engine/Tyre

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