R56 Mini First (1.4) lumpy idle - MINI Cooper Forum

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post #1 of 3 (permalink) Old Feb 27th, 2014, 09:31 PM Thread Starter
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R56 Mini First (1.4) lumpy idle

My wife has a 59 plate Mini First which had elevated HC readings at the last MOT, but the re-test just scraped under 200 ppm.

Her Mini has started idling lumpily (~650 - 700 rpm) and sounding a little raspy at low revs (< 2500).

I stuck my OBD cable on this evening and the o2 sensor seemed to be reading < 1v which seems a little low to me, I was expecting >= 1.5v (see attached*)

After reading h t t p://w w w.mini2.com/forum/second-generation-faults-fixes/206833-mini-failed-emissions-test-second-time.html I'm tempted to get some cleaner for the cat, but are my o2 readings out of whack or am I miss-reading them?

(*columns are: PID, sensor, current reading, units, min, avg, max)
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post #2 of 3 (permalink) Old Mar 5th, 2014, 01:15 AM
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Had a similar problem with our 2007 1.4 R56 70k miles which seems to be fixed now.

There were no OBD fault codes but we had a lumpy idle and slight hunting up and down with a flat spot at 2k-3k rpm and CO and HC emissions were both above MOT test limits.

It was time for a service so it had an oil change with new oil, air and fuel filters and a new set of plugs - which did not improve things.

We checked for an unmetered air intake leakage. Nothing found.

Next the throttle body was given a thorough internal clean. RESULT! - the CO reading reduced by 75% and HC's by 60%, well inside the MOT requirement.
It idles much better now and the flat spot disappeared.

I hope this helps with your problem.
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post #3 of 3 (permalink) Old Mar 16th, 2014, 04:42 PM Thread Starter
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Thanks for the advice

Finally got a good enough day with some spare time to have a spanner...

Replaced the air-filter and went for a run out; the car ran less lumpily, but ended up with a P1111A being thrown, so I think I need to clean the lambda sensor (and the throttle body while I'm doing it) and see if that makes things better
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