Hesitation disapearing when CEL on (code 2, O2 sensor)

[asylum]

Took my car for a ride. I noticed hesitations. It does not seem to be misfire. The hesitations appear only around 2500 rpm when I am at a constant speed and give slightly more gas to accelerate very gently.

A CEL code 2 appeared and desappeared the next time I started the car. The car ran perfect when the CEL whas on (default mode ?) and hesitated again with no CEL.

I am leaning toward a wrong O2 sensor as the car ran well on default mode. Can you confirm ?
Should I confirm that by pulling the O2 connector and drive with the CEL on to see the hesitations disappear ?

 

[Lude_2_NSX]

I got an occasional CEL for an o2 sensor lean condition, this was also accompanied with a hesitation. The cause was actually a failing fuel pump not delivering enough pressure. Once I replaced the fuel pump, fuel filter and cleaned the injectors, I can good fuel pressure and no more hesitation or CEL.

 

[asylum]

I learned about this fuel pressure problem. The thing is that the hesitations do not appear under strong acceleration but only when I accelerate very gently, so when I do not need a lot of fuel. But I keep that in mind.

 

[Larry Bastanza]

Sounds like a fuel problem for sure. Check pressure, if OK, I have cured this a few times by having the fuel injectors cleaned and balanced. RC engineering does a great job.

Regards,
LarryB

 

[jwmelvin]

Wouldn't a failing O2 sensor manifest as a fueling issue when under closed loop (light throttle, lower rpm)? When you are open loop (CEL), things are fine, which suggests to me that the fuel system is okay. Pulling the O2 sensor forces closed-loop operation and if the problem is really the fuel system, one would think the problem would remain.

 

[asylum]

Yes right. That is why I will check if the problem disappear if I pull the rear O2 sensor connector. If not, I will check the fuel pressure.

- - - Updated - - -

I realised that one of the bolts connecting the DC Sport header to the cat was loose resulting, I think, in a leak. Tightened it and went for a ride. No more hesitation. As the O2 sensor is 1'' from the connection, it seems it disturbed its reading.

 

[Lude_2_NSX]

Glad you figured it out!