General limp mode with no ecu codes

[smokingblue]

Hi, as a newbie I must apologise if this has been answered elsewhere but my Multipla 1.9 diesel, which has about 80k on the clock, goes into 'limp mode' if I go above certain speeds. I first noticed it when breaking the national speed limit in 5th gear. I believe this is rev related as it now happens in any gear when I push the speed. The strange thing is that although the engine management light comes on and it goes into 'limp mode' when it is connected to a diagnostic computer there are no fault codes shown, turning the ignition of and restarting seems to reset things and apart from this the engine pulls like a train. I've a sneaking suspicion that it might be down to the crankshaft sensor, as I have had this before on a Vauxhall, but the fact that there is no fault code showing up is disconcerting, so could it be just a MAFF, again I've had this as a reported fault on a Vauxhall, you see a pattern emerging here - I used to run Vauxhall Omegas (petrol), but this fault actually turned out to be the throttle body, so I don't necessarily believe what the ECU fault code gives as the problem, it's often only the first link in the chain. Enough rambling, if anyone has experienced the same problem or knows the answer please advise before I get into spending any serious money.
P.S. i am going to try checking the white connector in the line from the throttle potentiometer to ECU first to see if it's a 'throttle position' related fault, but I don't hold out much hope.

Thanks for any advice

 

[Bix67]

Disconnect the MAF sensor , if this cures it - it will need cleaning or replacement. It does no harm running with the sensor disconnected in normal weather conditions