I am after some help/advice regarding towing.

I've got a my08 TDV8 HSE when we drive solo we average 25 mpg running around and 27/28 on a run.
With our twin axel caravn on the back we average 21/22 mpg.
Last week on the way back from cornwall i had SYSTEM ENGINE FAULT come on about 6/7 times if i stopped turned off the engine the fault cleared. It hadn't done it before and hasn't done it since we have returned home and there are no faults stored. The car also only managed 15.6 mpg.

Has anyone got any idea what could be causing this?

What MPG do other members get from there cars when towing?

As you can imagine driving up the hills on the A30 and the car flags up this fault and you lose power with a 26 foot caravan on the back is quite scary


Many Thanks in advance

2200kg MTPLM Twin Axle behind my 3.0l and get 21/22 mpg towing so similar to yours but our towing 'styles' may not be similar which can have a massive effect, of course, on consumption. Soz - can't help on the fault code.

Surprised no fault codes ? Where did you take it to find that out/what reader or tool did they use ? Could be any one of a number of things. Clearly the car ain't happy or it wouldn't keep pinging up the fault. Even if it has now gone away the warning seemed linked to the extra towing load which needs checking out. You don't want it doing this again with a load on the back.

We have had similar issues in Aust and my 2.7 suffers the same.

It would seem to be basically an ECU programming fault in the software and the fault shows up when inlet manifold pressures are different to what the ECU is expecting - response from the car is either shut down, limp mode, nothing but the engine light comes on.

See if this is a similar scenario to what you have.

Drive the car around every day - car might be loaded up - use a bit of throttle - make the car work but no issues like you describe (manifolds pressures are what the ECU expects).

Now connect up your caravan (I have a campervan) and drive it sedately - no full throttle, no real big hills and nothing happens.

Now head up a big hill, use a lot of throttle maybe flat to the floor so the engine is really loaded up and the issue pops up (manifold pressure is not what the ECU expects)

Maybe straight and level towing that van and sitting on your 60mph just idling along on a secondary road - a slowish vehicle ahead and you go to overtake but that oncoming car is still a safe distance but a bit closer than expected - foot to the floor to use those V8 horses and the gong gong gong the fault light is on - pull over switch off and on and all good most likely no codes. I have learnt how on the freeway to switch into neutral, switch the engine off and back on before you loose steering and brakes and continue on my way.

Even when towing but not using a lot of throttle the problem does not occur. Lots of throttle creating high engine loads because of the 2 tons you are towing and gong gong gong.

It is if when they wrote the computer software they wrote it to suit the car without a requirement to tow anything.

So if at all possible when towing I just try not to get into positions where the throttle needs to go to the floor - often easier said than done. Mine is a 2.7, plenty of people report it in 3.0s and TDV8s BUT not any of the petrol V8s.

Garry 07MY RRS TDV6
Arctic Frost
Aspen Interior

Thanks for the responses
Is there a software update available to sort this or is a remap a better option where throttle response and setting are altered
Cheers Ade

I have a BAS remap and it made no difference. 07MY RRS TDV6
Arctic Frost
Aspen Interior

Never noticed it on my TDV8 when towing but then I was always gentle with the throttle - live cargo in the form of horses tends to make one go gently.

It might be worth checking the intercooler top hoses for any splits. Also give the MAF sensors a clean (carefully!). 2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed

Great thanks
Are the maf sensors the ones connected to the air filter box? and if so how best to clean them.

Thanks Ade

Mass Air Flow (MAF) sensor or Manifold Air Pressure (MAP) sensor?? - I would have thought the MAP sensor but cleaning both may help. Care is needed with both so not to cause damage. 07MY RRS TDV6
Arctic Frost
Aspen Interior

I towed a large PRG enclosed trailer last week. Been averaging 29 mpg on the computer. Dropped to 19 mpg, but no engine fault issues.

I did notice when towing the trailer made the Sport bouncy on some road surfaces. 2010 3.0 TDV6 RRS Overfinch GTS
1987 BMW E30 M3 2.4 Turbo
1990 BMW E34 M5 3.6 Trackcar