TD5 power loss when reached 85MPH and slows down to 70MPH

I have a standard TD5 with a alli sport intercooler and egr valve blanked off.
When I go out for a spin I warm the Landy up on a stretch of motorway.
I can accelerate up to 85MPH the first time but the engine seems to hit some sort of problem and slows down to about 70MPH and then it is slow to accelerate after this and will not reach 85MPH again. I have to pull in and switch off the engine and then start it again and then it will reach 85MPH but again only for the first time and then the problem repeats.
Any idea's (yes I know I'm lucky to reach 85MPH and it's above the legal speed limit).

id look at the waste gate on top of turbo see if it moves easily ,can be done by disconnecting rod or using airline to carefully pressurise actuator

Thank you James I will have a look now.
Cheers Les

how is the level of coolant in your tank? ... it looks like the ECM goes into overheat protection to me... is the temp gauge behaveing normally? watch it while this happens cos if it goes above the middle then that's the problem, which might be caused by a faulty temp sensor too or non locking viscous fan

the real diagnose would be to plug in a tester and read live data while this occures...i know that's not the best answer for you but that's a fact

You have an over boost problem, the ecu is going into safe mode. Have a look at the small pipes to boost control solenoid. It would be best to check boost pressure to confirm your fault, either read boost through live data or fit a manual boost gauge and have a look at peak boost.

rottenbucket said:

You have an over boost problem, the ecu is going into safe mode. Have a look at the small pipes to boost control solenoid. It would be best to check boost pressure to confirm your fault, either read boost through live data or fit a manual boost gauge and have a look at peak boost.

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Classic overboost. Caused by sticking wastegate or you have dialled up the boost too much. To run higher boost pressures on a TD5 you need to fool the ECU into thinking the boost is lower than it actually is. Much more than 1Bar on a TD5 switches the ECU into limp mode until you recycle the ignition. You can get boost boxes that plug into the ECU. I have one but it was too expensive to take apart and see what is actually in it. I suspect not a lot other than a few resistors and a capacitor but who knows? All the while it works I'll leave well alone.

+1 on stuck wastegate - heat shield off I found easiest, then disconnected the actuator rod coming from the 'pressure can' (whatever that is called!) and just worked oil into the swivel on the turbo top casing. Took a while to free up, but worked a treat after that - should turn with light finger pressure, not the mole grips and bulging veins needed when I first attacked it.

3 years later getting the occasional 'limp' at full bore - reckon its time for another visit in there..... Good luck.

(friend's diagnostic did show 1.5 bar - istr limp kicks in at 1.4....?, but do the wastegate first as its easy and free, if that doesn't do then move on to something else....) A