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Impossible to hold RPM when in neutral to 3000. Have P0420.
hi all,
I am facing a weird problem with my 2005 Maxima. I have a P0420 code and was trying to monitor O2 sensor values when the engine was hot. While trying to do that, I wanted to hold the engine rpm to 3k. The car was in neutral. The trouble is, I simply couldn't do that. My Maxima idles at around 800 rpm in neutral. I could press the gas pedal to bring the rpm up to 2k. But then just a slight little push and it slowly went all the way up to 4.2k. Release the pedal a little and it came back to 1.8k. Don't know if that is somehow connected to my P0420 code. Interestingly, I got the following graph going down from 4.2k rpm to 1.8k rpm for O2 sensors.
Bank1: upstream and downstream O2 : First row in the picture below
Bank2: upstream and downstream O2. Second row in the picture below
When at 4.2k rpm, the upstream O2 sensors were pretty much hovering at around 0.6v for bank 2 and 0.3v for bank1. Don't know why they are not the same values.
At the same rpm, the downstream O2 sensors are hovering at around 0.8v
As soon as I let do the throttle and the A/F mixture becomes lean, both downstream O2 sensors go down to 0.2v initially. Bank1 sensor stays at 0,8 a little longer than Bank2 but within a second or so, comes down to 0.2 and then both start climbing to 0.8v.
A little context:
At cold start, both downstream O2 sensors are at 0.3v till the engine warms up and then they both climb to 0.8v and stay there. At the same time, the upstream O2 sensors are at 0.3v for Bank1 and 0.6v for Bank2.
As engine heats up, both downstream O2 sensors start reaching 0.8v and stabilize there. For upstream O2 sensors, Bank1 stays at 0.3v and Bank2 at 0.6v
As I press the pedal and take rpm to 4.2k, the downstream O2 fluctuate a little but stabilize at 0.8/0.9v. The upstream swing a lot but then again settle at 0.3v for Bank1 and 0.6v for Bank2.
I used a android phone to capture the screen shots. So I don't have frame by frame data. I suspect the Android app averages the readings.
Can someone please help ? I am no longer sure if the pre-cat is bad. I don't smell rotten eggs in the exhaust even at 4.2k rpm. I need to get the car smog checked soon. Urgent help would be appreciated.
