Fuelsys2 N A

[Charise Farag]

Thecar is a 2002 ford focus 1.6 petrol. last week noticed that I could smell the CAT (sulphur) but it went and the car was running ok. Today, the idle has gone weird! If I take my foot off the juice it idles at 2500 RPM for about 30 secs then drops to 1400 RPM. This happens everytime I touch the accelerator. The car drives ok otherwise. There are no warning lights and my OBD scanner shows no codes. I can find no vacuum leaks or loose wiring. Any idea where to start? It has been suggested that it might be a failed O2 sensor or the MAF sensor. How can I check?

My scanner shows some live data but not fuel trims (whatever they are!) it does however say that it couldn't check the status of the CAT due to an open loop (I think) though there are no DTC codes and the engine check light stays off.

'Open loop' means the engine is running on a preset map without the lambda sensor feedback - it does this when cold as normal, but if the engine was warm and it was still running in open loop you may have a lambda fault.

Hot or cold is the same. I'll have to look up how to test the lambda sensors, there is one pre and post cat. I think my adaptor is an ELM 327 which should work. I use Torque on my phone. I'll download Forscan and try it when the rain stops!! Thanks.

Yes I have and it made no difference. I have now installed the Forscan software and it is a good piece of kit, thanks. I would be obliged if I could draw on your collective experience in interpreting the results. Fuelsys1 shows closed loop, bank 1, which I think is ok and applies to the pre-cat sensor (green) but fuelsys2 shows as error on bank 2 , I think this refers to the post-cat sensor (blue) see pics. Am I reading this right? If this is the only thing I will be a happy guy! There is still no engine check light and no DTC detected by Forscan. Thanks for you time guys, I really appreciate it.

I did look for a leak but I note the tail pipe is a little sooty rather than running lean. Also, the car drives perfectly well, no loss of power etc. It's just the very high idle that is troubling me.

The problem continues! The Forscan diagnostics showed an error in fuelsys2 (see above) so I changed the secondary O2 sensor but this has made no difference at all. For good measure I have also removed, cleaned and checked the throttle body and idle by-pass valve too. I'm completely stumped now.

Your throttle position is at 18%, have you put your Accelerator pedal position data in too, to ensure it's not a faulty accelerator pedal? There may be two data items for the pedal - one going positive and one negative.

Thanks but from what I read bank 1 refers to the O2 sensor before the CAT and bank 2 refers to the one after. I don't think it's the pedal as the throttle butterfly opens and closes without sticking and there is no binding of the cable. Everything appears as it should be which is why I'm so baffled. The car starts and drives well other than this idle problem. I'm getting desperate now as my son is supposed to be taking his test in this car next week. Also, is 18% bad? Do you know what it should be at idle? Goggle doesn't seem to know!

Had a look on an RAC site and someone with the same problem said they managed to fix it on their focus by replacing the Crankcase pipe behind the throttle body? (They said it was a bit difficult to see but never said if the pipe was collapsed or split)

CASE CLOSED! I turned my attention to the TPS. Removed it to see if it needed cleaning etc but when it was off it was obvious that it is a sealed unit with no access to the internal parts so I just put it back and everything is now fine! Must be about to fail so I am replacing it. What a pain, something so small causing me such a headache. I suppose we live and learn. Many thanks to all who offered advice, it was much appreciated.

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