Hello everyone

i have a mk2 focus 1.6 77k miles today i bought it about a year ago and within 200 miles the eml came on I plugged a scan tool in and was pointing at the cat, downstream o2 sensor was erratic . I contacted the car dealership and arranged for them to check the fault and they changed the downstream sensor and after driving around 50 miles the same code came up so returned the car and the company replaced the cat at no cost to me as I know my rights . I collected the car and no more eml has came back on now 1000 miles down the road . Today I decided to get the parts for a service to complete myself  but first I plugged obd2 to check a few things and noticed that the downstream sensor was erratic and matching the pre cat sensor which was on my service parts list, I checked the map sensor and this seemed erratic, ignition on engine off 104kpa engine @ idle 38kpa which seems ok but increase revs to 2.5k 37kpa so I removed the map sensor and checked and cleaned it with correct cleaner and reinstalled it not connected to the loom so it would reset ….left it there over night and today I reconnected the sensor and took it for a decent run and now at idle it’s 33kpa 

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and now the revs at 2.5k and 25kpa and if I just blip the peddle goes to 102kpa for a split second then stable at 33kpa is this normal or should I see the kpa increase as the revs are held at 2.5k 3.0k has anyone got any knowledge of this subject please 

thank you 

 

You need to check the Throttle Position at the same time, which is a different thing to the Accelerator Position and do so when the car is being driven.

You can rev the guts out of a stationary car and most of the data you get for what is driving the Engine will be completely different to when the car is actually being driven.

The Idle figure you have posted looks fine. 

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and now the revs at 2.5k and 25kpa and if I just blip the peddle goes to 102kpa for a split second then stable at 33kpa is this normal or should I see the kpa increase as the revs are held at 2.5k 3.0k has anyone got any knowledge of this subject please 

thank you 

Thanks for the reply I will record the live data on scan tool soon and check the values and report back hopefully with screen shots or the data, I can see a difference since cleaning the map sensor. I was always going to change the pre cat sensor at the service to keep them inline with age and miles 

thanks again 

Good morning 

got an update on data and seems fine I think ,some are under load and on over run as seen on rpm the car is an automatic.

since cleaning map sensor the car seems more responsive but still have the erratic downstream 02 sensor ,checked for leaks around engine bay none found got o2 sensor on order list 

my scan tool has a short data storage capacity so no graphs just each page screen shots 

thanks for any input on the results