Hello all!

I've been dealing with this code with a 2008 Fit I just bought.

For those who might not know, this code means the car is running rich. I've:

- changed the 2 O2 sensors
- changed the CAT since it was an EPA one but I'm in CA so I needed a CARB legal one
- changed the fuel injectors
- replaced a torn rubber connector/hose from the air box to a metal line

What I notice:

- fuel smell
- live data from scanner shows -31% short-term fuel trim at idle, causing the long-term fuel trim to quickly drop at idle. Driving fuel trims seem relatively normal (?)
- live data shows upstream sensor at around .1 to .2 mA at idle, Lamda is around .99. From some quick research, anything above 0 mA means the sensor is detecting rich conditions. The Lamda is pretty close to the expected 1.
- live data shows downstream sensor at around .8 ish
- live data shows intermittent EGR error of 99.2%

My thoughts:

My initial thoughts were o2 sensors and cat, but the code remained. I changed the fuel injectors since I was thinking maybe the old ones were leaking or spraying too much fuel. In the process of changing the injectors, I was checking for any cracks, etc to the intake manifolds and noticed the hose that was torn so I replaced that in case of a vacuum leak. I am thinking a bad fuel pressure regulator can be causing too much fuel to be sent. I've also seen that a possible cause for a rich condition at idle can be caused by a stuck open thermostat because the car thinks it's still in cold start conditions and will pump more fuel than required, but the car doesn't exhibit other symptoms of a stuck-open thermostat. I was also thinking about either a vacuum leak (intake manifold gasket, etc) or an exhaust leak before the upstream O2 sensor, but I'm seeing folks say that would most likely cause lean conditions instead of rich so not too sure.

What I planning moving forward:

- I have a new EGR valve on the way. The EGR error has been more consistently at 0% so I'm not sure if I'd need it in the end, but the 99.2% does still happen
- possibe fuel pump replacement. The fuel pressure regulator is integrated and can be changed without changing the whole pump but I think might as well replace the whole assembly.
- maybe take a look at the thermostat.

Sorry for the long post, but just wanted to see if anyone had any other ideas or had previously struggled with this code?

Thanks!

 

Have you checked the spark plugs? A fouled plug could be causing incomplete ignition which would lead to unburnt fuel being sensed.