German Car Zone

Limp mode is a broadly used term for any deliberate reduction in engine output by the electronic control unit when a certain engine parameter is breached. This is done to prevent catastrophic mechanical failure.

In turbo'd cars it is a much more common occurence. In such cases turbo boost, max rpm, throttle position and so on can be restricted in order to avoid mechanical engine damage. Modern electronics is one of the reasons that turbocharged engines are so much more reliable these days. Because turbo'd engines need to operate within more carefully balanced conditions, as soon as a certain parameter such as air mass, exhaust gas temp etc. get exceeded, the engine management system can restrict the load on the engine by tapping off boost completely.

But, if the ECU programming tolerances are too fine then limp-mode can occur without there being a proper reason and this translates into a very frustrating driving experience. Ask me. I know all about it. And, every time the problem was solved via an ECU re-flash. Software parameters protect a turbo'd engine - no doubt. But, they can also be an unnecessary interference.

Today morning a co-worker was complaining from the same symptoms. Not to mention that he never went on track or heavily used his car. I think an ECU relfash is required. His car is like mine, X6 3.0 TT

Thanks again martin.

Bear in mind of course Sayyaaf, that an ECU software upgrade ("re-flash") is only applicable if there is a software program update available from your local dealer. If not, then re-flashing the ECU will have no effect.

Another thing to consider is that one of the instruments used to feed the ECU with measurements of air mass, throttle position, knock, lambda etc could be faulty and sending through incorrect measurements that fall out of the programmed tolerances in the ECU software.

BMW already had this problem when 335i came to the market. I'm pretty sure BMW had a recall about this in US.

If memory serves me right, BMW added a oil cooler to the 35 engine after similar problems with heat build up and may be even retrofitted it to existing cars. May be they will do the same to the V8.

IMO BMW still got a an experience to acquire with FI engines,i never heared about MB or Audi having such problems.Or did they? not sure but ASAIK i didn't come across anything..anyone

Trust my, there been owners with Audi Turbo problems. Neither Audi or MB engines are flawless. Besides BMW been using Diesel Turbo engines for many years now.

I know about those Audi owners having problems with the 1.8T engine but come on we all kmow that Audi has much experience with turbod petrol engines than BMW.

As for MB i haven't came across any thing yet

And i was talking about petrol engines not diesel.

Just because you dont hear about it, doesnt mean it doesnt exist.
If you think MB engines are going and going and never goes wrong then you live in a Utopi.

Heat soak effects most aspirated engines especially large ones. Previous RS6 was notorious for it. So is MB 55 and 65 engines. That is why adding larger after market intercoolers is one of the most popular mods for aspirated engines.