Check Engine Light codes

[Trident]

Help required please. Today is my last chance to get the car ready for Japfest and having passed the MOT (don't know how!) the engine has decided to misbehave. I connected a jumper wire to the Service Check-Connector to try and read the codes, but all I get is a constant short blink every 2 seconds with no variation.
Any ideas?
Trident

[Sudesh]

This is on prime, not sure if there much if any differences in US and other regions.

http://www.nsxprime.com/FAQ/DIY/trouble_codes.htm

[Kaz-kzukNA1]

Hi, Trident.

It would be nice if you can post bit more detail of your NSX.
From your signature, I believe it is the 91 model and possibly the UK spec.
Mileage?
AT/MT?
Any modifications to the engine/Gbox?

Bit more detail on the ‘misbehave’ of the engine would be helpful.
At what rpm/speed did you notice the issue?
Is it continuous misbehaviour (i.e., the engine is still not running smoothly) or it misbehaved just once at that point and since then, it seemed to be running fine even with the CEL (Check Engine Light or sometimes called as MIL, Malfunction Indicator Light) on the dash?


It would be nice if you can take video but sounds like you are getting CEL/MIL #1 or #10.

#1 is Front bank O2 sensor signal.
It is triggered by the abnormal reading of the A/F ratio and it has to be detected twice before the ECU decides to switch on the CEL.
Therefore, it could be triggered not just by the O2 sensor failure but also by misfire caused by the spark plug, fuel pressure, etc issue so needs to be bit careful with the diagnosis.

If your engine is running fine with the CEL ON (but with no other warning lights or other error code on the CEL) at the moment, then it is very likely to be the O2 sensor failure.

Under this condition, ECU will keep the system in Open loop control so your fuel economy would be worse and very likely the engine won’t respond as fast as it used to be.
Please note that the CAT won’t be working efficiently as it needs both the rich and lean cycle (Closed loop) to re-generate itself so not good for the CAT (and environment) from this point of view.


If the engine is not running smoothly even with the CEL (keep misfiring over any rpm range or below/above a certain rpm), you have other issues.


#10 is Intake Air temperature sensor failure but if this was the case, you will notice the change in idle rpm (rough or higher).

Enough as a starter.....

Kaz

[Trident]

Hi Kaz, Thank you for responding so quickly.
Yes, my NSX is a 1991 UK spec MT. 129960 miles.
Idle speed is high and variable. Car runs reasonably well for only half a mile then loses power. High fuel consumption and you can smell the unburnt fuel. O2 sensor has probably failed on the front manifold as you said but other issues as well. Did a temporary repair on the front flexible exhaust to get through the MOT. Spent the afternnon checking the plugs and coils which all seem fine although two of the rear coils are quite rusty as one seal was missing. Oil, oil filter and air filter were changed last week. The car has been idle for a few months although it has been run occasionally. Pete

[Sudesh]

Hi Kaz, Thank you for responding so quickly.
Yes, my NSX is a 1991 UK spec MT. 129960 miles.
Idle speed is high and variable. Car runs reasonably well for only half a mile then loses power. High fuel consumption and you can smell the unburnt fuel. O2 sensor has probably failed on the front manifold as you said but other issues as well. Did a temporary repair on the front flexible exhaust to get through the MOT. Spent the afternnon checking the plugs and coils which all seem fine although two of the rear coils are quite rusty as one seal was missing. Oil, oil filter and air filter were changed last week. The car has been idle for a few months although it has been run occasionally. Pete

Rust on the rear bank of coils seems to be a common enough thing. Mainly due to water coming in the rear vent and dripping down over the cover, plus old/perished seals. I managed to clean down and save some coils in the past, but some others had to be replaced.

There is only one seal on each of the coil covers, and obviously the seal should be at the top.

[Trident]

I will change the O2 sensors and front flexible exhaust pipe and then see how it goes. I will be coming to the show with Gary in his NSX so the tickets won't be wasted and there will still be the same number of cars. Kaz, when I'm ready I'll book in for a long overdue health check if that's ok with you? Pete