Car running rich - smells of fuel while idelling. Any ideas?
 

My car is running rich, it revs up a little when stopping at lights and idelling seems to run rich, even though it sits at 800 rpm. I can smell the fuel.

I have OBD2 diagnostic software, and have included a few pages of info. any help would be really appreciated.

I would ideally like to know what the average readings should be and then hopefully diagnose the problem. What should the long term fuel trim readings be? etc.

Cheers,

Paul

On p.1 it shows that your fuel system is in open loop. If you took that screen shot right after you started the car, that is okay. If the car had been idling for a while before you took the screen shot, then there is something wrong.

It indicates that your O2 sensors are not used to adjust the mix, so your car runs off of generic tables, which may cause the rich mixture.

Let it idle for a while, check that it goes into closed loop, and observe if the O2 sensors are switching properly.

Hi there,

Thanks for the info. the photos were taken after a 15 minute run to work. I recently installed some Bosche universal O2 sensors that required me to splice into the existing wiring as they do not come with the connecting block, much cheaper than purchasing with them. I may have one or both of them not connected properly when I spliced into the wire. As it looks like the system is staying in open loop.

Is there any way of seeing which one may be badly connected? on Page 3 when I am driving the sensor readings change. (mine is an old 99 plate boxster - only has 2 02 sensors - pre cat.) The readings changing on page 3 (sensor 1 - bank 1 & sensor 1 bank 2), do change they sit at 0% at idle, but change whilst driving.
Is this data read from the ECU or feedback from the Sensors?

Alternatively is it as easy as - if the system goes to closed loop then the O2 sensors are working?

On page 1 , is fuel system 1 status, representing one O2 sensor and fuel system 2 status representing the other one, in other words by having both systems stating open loop does it mean that both my sensors are not working?

Appreciate the info and the help.

Kind regards,

Paul.

Yes, looks like neither of the O2s is working. Even at idle your scan tool should report switching voltage; e.g. the O2 voltage should sweep between approx. 0.2V and 0.8V. O2 sensor output is not a percentage, it's a voltage between 0 and 1V.

So yes, something didn't go right when the O2s were changed...

Many thanks Fluellen,

Great, clear concise information, I shall tuck the car away as I am away this weekend, but shall work on it Monday as I have next week off work.

Hopefully all will be fine after i re-wire the sensors. fingers crossed.

You're welcome! Hope it works out!

hi,

I am half way through replacing the sensors, will continue with the other tomorrow morning, I am wondering if the car stays in open loop, could the air sensor be to blame?

If so, can someone tel me where it is , how easy it s to replace and importantly would this working incorrectly make the car run rich and in open loop?

Many thanks

Paul