Rough idle, sooty exhaust

suzublu · 15th November 2021, 12:54

As above, already changed the plugs, runs fine, thinking IACV or a sensor? Ideas gratefully received

1.8 NA btw

Yorkshire GOC · 15th November 2021, 15:23

sounds like she is running rich - any codes - maybe a dodgy O2 sensor

suzublu · 15th November 2021, 15:54

Quote:

Originally Posted by Yorkshire GOC

sounds like she is running rich - any codes - maybe a dodgy O2 sensor

Put the P-Scan on and no errors Martin

Ran the live data and loads of numbers on each parameter, unfortunately, I don't know the correct readings

Runs fine, just a little lumpy on tickover. I'll change the coil packs and leads as I've got some from Matty

Yorkshire GOC · 15th November 2021, 16:01

Would expect misfires as well for faulty coil packs/spark plugs - do the 02 sensor readings for the pre and post cat look OK ?

suzublu · 15th November 2021, 16:05

Quote:

Originally Posted by Yorkshire GOC

Would expect misfires as well for faulty coil packs/spark plugs - do the 02 sensor readings for the pre and post cat look OK ?

No idea what the correct readings are supposed to be

Yorkshire GOC · 15th November 2021, 17:39

Very simply the pre cat sensor should show a reading that fluctuates with a wildly varying waveform between 0.1 volts and 0.9 volts as the mix fluctuates between lean and rich (lean =low v and rich = high v) once it passes through the cat the impurities are removed and an ideal reading for the post Cat 02 is 0.45 (the perfect air fuel ratio) - very simply The o2 sensor's voltage should fluctuate within the 100mV – 900mV (0.10V to 0.90V) range. If it is within this range, the o2 sensor is operating normally if they are not within this range, there is either an engine problem (eg loose hose) or the o2 sensor is bad. Also the post cat waveform does not fluctuate as wildly as the pre cat waveform. Your OBD tool should be able to show this as part of real time monitoring.

Yorkshire GOC · 15th November 2021, 17:41

Is your Cat after market or original ?

suzublu · 15th November 2021, 18:07

Quote:

Originally Posted by Yorkshire GOC

Very simply the pre cat sensor should show a reading that fluctuates with a wildly varying waveform between 0.1 volts and 0.9 volts as the mix fluctuates between lean and rich (lean =low v and rich = high v) once it passes through the cat the impurities are removed and an ideal reading for the post Cat 02 is 0.45 (the perfect air fuel ratio) - very simply The o2 sensor's voltage should fluctuate within the 100mV – 900mV (0.10V to 0.90V) range. If it is within this range, the o2 sensor is operating normally if they are not within this range, there is either an engine problem (eg loose hose) or the o2 sensor is bad. Also the post cat waveform does not fluctuate as wildly as the pre cat waveform. Your OBD tool should be able to show this as part of real time monitoring.

Quote:

Originally Posted by Yorkshire GOC

Is your Cat after market or original ?

That's perfect Martin, thanks

Aftermarket cat fitted about 4 years ago

Yorkshire GOC · 15th November 2021, 18:35

All i would say is after market cats are notorious for not being up to scratch but you would expect an inefficient Cat to generate a PO 420 or 430 code on your code reader. I would look at the O2 sensors - they may still be working but are "sluggish"

Yorkshire GOC · 15th November 2021, 18:39

And make sure you do the readings when your engine is up to temperature - for the first few minutes from ignition the sensors do not work that's why on a classic cold start morning your exhaust can smell rich - they need to be at temp.

15th November 2021, 12:54	#1
suzublu This is my second home rover 75 1.8 vvc club se wedgwood blue Join Date: Aug 2009 Location: Seaton Carew Posts: 26,936 Thanks: 65 Thanked 7,142 Times in 4,642 Posts	Rough idle, sooty exhaust As above, already changed the plugs, runs fine, thinking IACV or a sensor? Ideas gratefully received 1.8 NA btw

15th November 2021, 15:23	#2
Yorkshire GOC I really should get out more....... Rover 75 connoisseur se v6 auto Join Date: May 2014 Location: Hull Posts: 2,069 Thanks: 1,842 Thanked 623 Times in 469 Posts	sounds like she is running rich - any codes - maybe a dodgy O2 sensor __________________ She came off the Longbridge Line on 20-05-2003 The Silver Machine was the 13th of 160 Rover 75's to come off the production line that day and is the 100th of 527 Starlight Silver Rover 75 2.5 V6 Connoisseur SE Auto saloons listed in the build records produced world wide.

15th November 2021, 16:01	#4
Yorkshire GOC I really should get out more....... Rover 75 connoisseur se v6 auto Join Date: May 2014 Location: Hull Posts: 2,069 Thanks: 1,842 Thanked 623 Times in 469 Posts	Would expect misfires as well for faulty coil packs/spark plugs - do the 02 sensor readings for the pre and post cat look OK ? __________________ She came off the Longbridge Line on 20-05-2003 The Silver Machine was the 13th of 160 Rover 75's to come off the production line that day and is the 100th of 527 Starlight Silver Rover 75 2.5 V6 Connoisseur SE Auto saloons listed in the build records produced world wide.

15th November 2021, 17:39	#6
Yorkshire GOC I really should get out more....... Rover 75 connoisseur se v6 auto Join Date: May 2014 Location: Hull Posts: 2,069 Thanks: 1,842 Thanked 623 Times in 469 Posts	Very simply the pre cat sensor should show a reading that fluctuates with a wildly varying waveform between 0.1 volts and 0.9 volts as the mix fluctuates between lean and rich (lean =low v and rich = high v) once it passes through the cat the impurities are removed and an ideal reading for the post Cat 02 is 0.45 (the perfect air fuel ratio) - very simply The o2 sensor's voltage should fluctuate within the 100mV – 900mV (0.10V to 0.90V) range. If it is within this range, the o2 sensor is operating normally if they are not within this range, there is either an engine problem (eg loose hose) or the o2 sensor is bad. Also the post cat waveform does not fluctuate as wildly as the pre cat waveform. Your OBD tool should be able to show this as part of real time monitoring. __________________ She came off the Longbridge Line on 20-05-2003 The Silver Machine was the 13th of 160 Rover 75's to come off the production line that day and is the 100th of 527 Starlight Silver Rover 75 2.5 V6 Connoisseur SE Auto saloons listed in the build records produced world wide.

15th November 2021, 17:41	#7
Yorkshire GOC I really should get out more....... Rover 75 connoisseur se v6 auto Join Date: May 2014 Location: Hull Posts: 2,069 Thanks: 1,842 Thanked 623 Times in 469 Posts	Is your Cat after market or original ? __________________ She came off the Longbridge Line on 20-05-2003 The Silver Machine was the 13th of 160 Rover 75's to come off the production line that day and is the 100th of 527 Starlight Silver Rover 75 2.5 V6 Connoisseur SE Auto saloons listed in the build records produced world wide.

15th November 2021, 18:35	#9
Yorkshire GOC I really should get out more....... Rover 75 connoisseur se v6 auto Join Date: May 2014 Location: Hull Posts: 2,069 Thanks: 1,842 Thanked 623 Times in 469 Posts	All i would say is after market cats are notorious for not being up to scratch but you would expect an inefficient Cat to generate a PO 420 or 430 code on your code reader. I would look at the O2 sensors - they may still be working but are "sluggish" __________________ She came off the Longbridge Line on 20-05-2003 The Silver Machine was the 13th of 160 Rover 75's to come off the production line that day and is the 100th of 527 Starlight Silver Rover 75 2.5 V6 Connoisseur SE Auto saloons listed in the build records produced world wide.

15th November 2021, 18:39	#10
Yorkshire GOC I really should get out more....... Rover 75 connoisseur se v6 auto Join Date: May 2014 Location: Hull Posts: 2,069 Thanks: 1,842 Thanked 623 Times in 469 Posts	And make sure you do the readings when your engine is up to temperature - for the first few minutes from ignition the sensors do not work that's why on a classic cold start morning your exhaust can smell rich - they need to be at temp. __________________ She came off the Longbridge Line on 20-05-2003 The Silver Machine was the 13th of 160 Rover 75's to come off the production line that day and is the 100th of 527 Starlight Silver Rover 75 2.5 V6 Connoisseur SE Auto saloons listed in the build records produced world wide.