I notice that my 2011 TDV8 4.4. has difficulty above 30 °C (86 °F). The air conditioning is full power on and I notice that when I release the gas the car slows down more quickly than normal. It seems like there is a restriction or something makes me slow down quickly. Besides that I can drive fine, no error messages. Touching the accelerator pedal does not go smoothly. If it is cooler then nothing is wrong, only in a warm environment. It seems that the air conditioning pump has influence because this also happens when I switch on the seat ventilation so this related to het A/C. Someone experience it because there are enough people here in other warm countries. Maybe I should replace something.

I believe the seat cooling is handled by peltier pump so not connected to aircon at all, they will however present a substantial electrical load. It seems from what you've said you notice that the engine is under additional load when its hot either by aircon, seat cooling or both which may make sense. Have you had the aircon gas checked recently? if it's low the compressor will work harder to cool the car, if there's too much it can present an immense load to the compressor and onwards to the engine. BMW i3 Electric Car
2012 Full Fat RR 4.4 TDV8 (now gone)
2006 VW Touareg 3.0 TDi V6

Hi, roel2018

I too notice this behaviour in the summer. Although, it’s irrespective of the AC/cooled seats.

Firstly, the car will rev at a higher RPM without any input from the accelerator pedal. Up to maybe 1,000 RPM. It seems to do this on a timed cycle, with the increased revs only being held for a few mins. She does this whether the engine is hot or cold so I assume based on ambient temp and to get the fans working.

Secondly, when it’s proper hot 🥵 (40+ last week...) the car won’t upshift into 8th gear unless at proper highway cruising speeds. Sometimes I try to override it using the paddle and I am given a polite “no” as it remains in a lower gear. Again, I assume it does this to keep cool? In a similar yet opposite way it does in the winter, the gearbox won’t upshift until it can ensure its warmed up properly and to aid economy.

But also, the ‘slowing down’ I describe it as almost like a dragging sensation, like the car is being held back by the gearbox. Take your food off the gas at low speeds (Town driving, etc) and you almost fall forward in the seat it’s that strong of a sensation, a bit like auto-engine braking. I can’t articulate it very well but it’s most odd. Only happens when it’s really hot. I’m sure Dodge Ram owners say something similar about this ‘box.

Hope that help, Tom. 2012 4.4 TDV8 Westminster - Baltic Blue, Jet interior
1997 P38 2.5 DSE auto & 1998 P38 2.5 DT Manual
1988 Vogue 3.5 EFI - Manual, gone.
2004 Volvo C70 2.0T convertible, had since new.
2007 Mazda MX-5 2.0 Sport Roadster/Coupé, had since new.
2024 Mini Cooper S cabrio, JCW kit, 2.0, DCT auto

AJGalaxy2012 wrote:

I believe the seat cooling is handled by peltier pump so not connected to aircon at all, they will however present a substantial electrical load. It seems from what you've said you notice that the engine is under additional load when its hot either by aircon, seat cooling or both which may make sense. Have you had the aircon gas checked recently? if it's low the compressor will work harder to cool the car, if there's too much it can present an immense load to the compressor and onwards to the engine.