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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 02

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The owner also told me that when he started the engine, instead of going through the warm up sequence, quite often, the engine rpm dropped and almost like about to stall.

Because of this, the owner wanted me to clean the TH butterfly as well while his NSX is at my place.

Before resetting the on purposely disconnected O2 sensor error from yesterday, started the engine as it is first thing in the morning.

Nothing unusual and the engine just fired up and kept going through the warming up period and settled to the idle rpm of about 800rpm after some time.


To get the base line feeling, test drove the car with Front bank Primary O2 sensor disconnected.

I actually didn’t feel so sluggish in the way the owner told me and quite normal for the DBW + LEV behaviour for AT model.

I normally use F-matic (if it is available) whenever I drive AT model but on this occasion, I on purposely kept it in ‘D’ range as this is how the owner was driving so far.







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Nothing unusual found so went back to my place, re-connected the O2 sensor, cleared the ECL error code using my mobile phone and another test driving session was carried out.

From this point, several PIDs were logged for each test driving session and then analyzed for further investigation.


As confirmed yesterday by the owner himself, despite re-connecting the O2 sensor and clearing the ECL, keeping the ECU in Open or Close loop control didn’t make any differences on the way the car behaved.

The four O2 sensor voltage were not shifted and once they were warmed up, the primary ones were oscillating at ideal frequency between lean and rich threshold at idle rpm as well as steady 70mph cruising mode. The secondary ones will stay at about 0.7V depending on TH/rpm conditions once warmed up and operating normally.

And although it was confirmed by the ECL error code, checked that all four O2 sensors were connected to the right ECU port as it was using extension cable due to aftermarket header installed.
On several occasions, some of the owners suffered fuelling issue due to Front and Rear primary O2 sensor connections being swapped.

The short term fuel trimmer were adjusting themselves accordingly and at this stage, the long term ones were not showing big figures so EGR issue or any air leakage after the intake manifold pressure sensor were very unlikely.


The intake manifold pressure sensor was reading the correct voltage before starting the engine (about 2.8V), at idle rpm (about 1.0V), on full throttle and so on.

I even measured the voltage with the multi meter to confirm the response against the TH pedal movement and there was no delay.

On later AT model, this intake manifold pressure sensor is also used for AT control so the signal input to the AT controller was also checked with no fault found.


While you are driving the DBW + LEV model, there is a certain delay factor added in the control loop for emission purpose and the engine rpm won’t respond quickly on acceleration or deceleration even on MT model at certain rpm range so you need to know this behaviour.

Even on 02 Type-R, you can feel this delay at low speed region.


The Intake Air Temperature sensor was also monitored with no strange signal found.

Automatic Transmission Fluid (ATF) level was checked immediately after stopping the engine and it was sport on. The colour was light dark red so quite normal for used AT unit.


Tomorrow, I’ll wash the TH butterfly, reset the ECU and drive on purposely in the traffic to simulate the similar driving environment as the owner.

Kaz
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Engine/Tyre

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