Is my O2 sensor going cold?

[b4black]

Over the summer I installed a set of headers and have been learning to tune with HPTuners. I'm running into a problem. From time to time, the oxygen sensor quits cycling and stays very lean. The LTFT's go very high as well. Seems to happen if it idles long or when driving at a light cruise.

When I first noticed this, I changed the O2 sensor with a new Denso unit. Didn't help. If anything, it's worse.

The headers are TOGS and the O2 sensor now sits a lot further downstream than on the stock manifold. Is the placement of the sensor too far downstream to keep it hot enough? I know the sensor is heated, but I can't figure out what else could be going on.

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[bikrboy128]

do you have any exhaust leaks?

 

[b4black]

The headers sealed up well as far as can tell. No sounds of leaks or any ticking noises. Only leak is where the downpipe meets the catback.

 

[Handsome Jesus]

Did you remove EGR and not remove EGR activation or something? I have not been in this situation, but the long cruise scenario might indicate it is trying to command EGR or something. Just a thought.

 

[Turbocharged400sbc]

evap is known to cycle at both idle and cruise

egr isnt as likely unless the egr valve is sticking open

or its just an idle issue and what your seeing at cruise is normal.

damn gremlins

 

[b4black]

EGR is still in place and working.

I know I have read that even with stock manifolds, that prolonged idle will allow the o2 sensor to cool and send the ECM into open loop. I assume with the headers and the sensor that much further downstream, it's even more likely.

When the sensor is working (switching), things look great and I started to dial in my LTFT's. But when I go for a drive these "cold periods" get collected by the histograms and throw the results off. If it happens long enough, the check engine comes on (lean code).

 

[Yaj Yak]

What year is the car?

 

[b4black]

2002 Regal GS