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ozzie1989

Member Since: 25 Feb 2009
Location: Wales
Posts: 282

2010 Defender 110 Puma 2.4 USW Bonatti Grey

Strange intermittent rough idle and clunk - any ideas?

Hi all,

Something I've noticed recently, more so after a long stint on the motorway for example, is that when I come to a stop the idle doesn't seem quite right. The audible sound of the idle changes gradually, from 'smooth' to 'rougher' (but does not knock) and then there is a large 'clunk' sound, the engine/vehicle shakes with this clunk, and it all goes back to normal. This happens over approx 5-10 seconds.

The clunk and associated shake of the engine and vehicle I can only describe as something like an A/C compressor clutch kicking in (albeit badly) but without the associated rev drop. Every time this has happened the A/C hasn't been on and when I do use the A/C the compressor comes on and off with a small change in revs, not a clunk.

I should say it doesn't happen all the time and up to now if it's happened once on a journey it doesn't happen again on the same journey.

Any ideas where to start? I had 4 new injectors, seals, VCV etc. 9-10 months ago, one could be bad an explain the poor idle, but the clunk?

All help appreciated

Now: 2010 2.4 TDCi 110 Utility Wagon
Then: 2004 2.5 TD5 90 Hard Top (X-Tech Edition)

22nd Sep 2019 7:47am

KelvinB

Member Since: 17 May 2018
Location: Crickhowell
Posts: 24

2008 Defender 110 Puma 2.4 CSW Stornoway Grey

Just had a similar thing. 200 mile journey on the motorway and when stopped at the destination had a really lumpy idle for a few seconds as if it was going to cut out but it then recovers.

Driving normally then engine is fine until you stop and then engine goes to idle again.

Did you ever get a solution to this ?

25th Mar 2021 8:31pm

custom90

Member Since: 21 Jan 2010
Location: South West, England.
Posts: 20348

Can you check for DTC’s via the OBD connector?

If the VCV was changed that recent it shouldn’t be that, possibly the clutch switch may be of interest but not guaranteed.
The former flags no DTC’s but the latter, may well flag up DTC’s.

A failing clutch switch can cause some weird issues, the clunk could be created by sudden changes in load and input to the engine.
The clutch switch affects various different running characteristics and vital responses for the ECU that can cause all sorts of performance related problems.

I’m not an expert, however, it’s possible that these things can be culprits. Cleaning the MAP and MAF sensors is worth doing too.
Or if money isn’t an object ideally if many years old replaced all together.

$W33T $0U7H3RN $UG4R
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25th Mar 2021 8:43pm

KelvinB

Member Since: 17 May 2018
Location: Crickhowell
Posts: 24

Cheers Steve.

MAP and MAF will be cleaned in the morning and codes checked. There should be some as the EM light came on.

I'll post an update when I know more

25th Mar 2021 9:08pm

custom90

Member Since: 21 Jan 2010
Location: South West, England.
Posts: 20348

Ah yes, if you’ve had the EML on the dash then that’s a sure sign there is a DTC or more present so you’ll be able to track the culprit down via that with any luck.

$W33T $0U7H3RN $UG4R
🇬🇧🏴󠁧󠁢󠁥󠁮󠁧󠁿🏴󠁧󠁢󠁷󠁬󠁳󠁿🏴󠁧󠁢󠁳󠁣󠁴󠁿🇮🇪🇺🇸⛽️🛢️⚙️🧰💪

25th Mar 2021 9:13pm

KelvinB

Member Since: 17 May 2018
Location: Crickhowell
Posts: 24

Solution

Turned out to be an oil contaminated MAF.

There's a breather tube that joins the air intake on the clean side of the filter. The breather tube joins the larger tube downstream and the airflow would normally dictate that the air coming from the filter and MAF would stop it getting contaminated but for some reason after a long journey it does.

Maybe the engine oil is evaporating travelling down the breather and then condensing in the larger tube.

Cleaned the breather and air intake, cleaned the MAF and it's now perfect.

I've seen others with this problem and one solution seems to be a catch can on the breather. Maybe a different oil would also help.

29th Mar 2021 9:00pm

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