Lumpy Feel After Idling For A Few Minutes

[Carl911]

I have noticed since the cold weather has started that if I have been driving for about 20 minutes and then come to a stop, the engine being up to temperature then the car sits at around 800rpm at idle and is fairly smooth as I would expect.

However, I noticed when sat in traffic stationary that after about 2 minutes the idle suddenly goes quite rough despite the idle remaining at 800rpm. I'ts almost like something switches after being stationary on tickover.

Has anyone else experienced this and any ideas why this happens.

Theres no fan coming on either so its not the fan cutting in causing the rough idle.

Car drives fine, no lights on dash and not really a big problem just that I have never noticed this before.

Carl

[Exdee]

Carbon buildup.

http://www.clublexus.com/forums/is-second-generation/484055-lexus-4gr-fse-engine-carbon-build-up-merged-threads.html

[normski2]

If you think it is. Perhaps chuck a can of BG44K through a tank full of fuel...may just help. Not a command.. just a thought... I lobbed a can thru mine after I got it...purely as a precaution. Engine is now silent stealth mode!!

[Exdee]

Only older cars have this problem. Reading through that thread one can see that the valves, pistons, direct injection engine and what not have been blamed for this. BG could be a short term solution but it will come back. Unless you do it like once a month which I am sure is not a good idea.

[Carl911]

I should of mentioned this is occurring on my 220d. I have just cleaned the EGR and put some bg44k through.

Mybe I've got so used to the 250 petrol that the diesel feels lumpy by comparison.

Carl

[Shepherd]

just to put it out there, please note that a lot of petrol stations don't switch to winter version of diesel straight away. This means that during early winter as the temperature falls the diesel may be gelling up a bit, causing strange idle behaviour and car smoking a bit as well. this happen to me last early winters and went away after a few weeks and didn't happen again till start of this winter (i.e all this week). I hope I am not saying something all stupid but that is what I was told was happening in some earlier post on this forum.