| In the car today, I was stuck in traffic on a hot day. After a few minutes (still at standstill), the revs at idle fell slightly and a judder started. This got worse until the whole car was being shaken - it was quite noticeable. Also, revs dropped further to about 500rpm. Pulling away, revs rose slightly lumpily - but eventually engine pulled as normal as revs rose above 2k. I checked under the bonnet when @i got home and the engine was shaking a fair bit. All this time, while the revs were lower than normal, they were not 'hunting' - it was a fairly even idle. Any ideas? (oxygen sensor??) | 
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