NAP1

I was just cruising back from my brothers through London. I was sitting in heavy traffic for a while and as the traffic cleared I accelerated in 2nd (at about 2-3krpm) and there was no power. The car accelerated but it was like it had suddenly become a 1litre or I had my foot on the brake.

It continued to do it for about 5 mins and then seemed to clear it itself. Some background:

Car is 100% stock.
Oil level is fine.
No warning lights came on.

Would the car sitting in really hot conditions in traffic upset the engine like this?

rahula

100% yes. It is very normal, the engine needs fresh air and being stuck in traffic during a very hot day will only make that air hotter from the engine/radiator.

NAP1

Thanks for that, will it cause it to run that badly for about 5mins afterwards before it sorts itself out?

rahula

Sometimes mate, in fact you could have been in any car and you would get a similar problem with power. Today was very hot and being stuck in traffic will cause this issue. It all depends on how much speed you got to before it cleared up but I can assure you there is nothing to worry about. It would take a while for the air in the engine bay to be replaced with outside flow and it all makes a difference. In the same way you will feel the car really powerful on a very cold day because the air is so much denser.

NAP1

Cheers for that, I can relax now that she is still OK.

rahula

go have a beer in the garden and take her out for a spin tomorrow.

Paper Lawyer

but five mins?!? I would have thought it would be more like 5 seconds?

adg1717

Thanks

You've also put my mind at rest. Same thing happened to me. Sitting in traffic yesterday, finally get some space, low revs, eg 2-3k and there's very limited power. Cleared up once i'd got some fresh air into her tho

mmm, good idea, sweet beer in the garden.

rahula

it's all relative Craig. Sitting in traffic and then mving off and going slowly doesn't allow much air in. If this was to occur all the time it would be different but we all know how hot it was today and it is very normal behaviour.

Spanners

High temperature, air heats and expands, fewer molecules of oxygen in any given volume that the engine tries to breathe in and so power output is lower. Converse, is that a cold day is good for power output.

However, this effect would lessen as the air under the bonnet cooled back to the outside air temperature. Still lower power but not so 'dramatic'

Is there a sensor that the ECU reads that holds back the power at all which could have got over heated and took a few mins to cool?