Wastegate playing games....

[Rmachines]

Ok first off, this is for my 98 MK3,  not my MK4.  As this is the closest forum to it regarding the TDI engine i came here.

I Had a fault code for ages and the engine would go into limp mode every time the car was taken above 60mph, turns out the hose that connects the ECU to the intake manifold was left disconected,  so i plugged it in for the first time since i had the car and sure enough, all faults gone and the car drives great... However when i accelerate to full throttle or near enough, the boost will hit 1.5 bar (i use a boost guage) then it will go down to 1, then back up to 1.5 etc..  its constantly fluctuating, i can hear the turbo slowing down and spooling back up when this is happening,   Im not sure if its normal or there is something else faulty?  It doesnt cause a problem, i can feel the power drop slightly on hills while its happening but im worried it probably wont do the wastegate/actulator much good if this is constantly happening?!? 

Any ideas what it could be?   cheers. 

[Rhyso]

hmm do you not have a boost control soleniod that actually controls the turbo actuator??

when your boost is spiking and then dropping on the MKIV's its normally down to that or the actuator itself sticking 

[Rmachines]

before it happend at full throttle up a hill it would hit 1.8 bar which was its absolute max,  now i have connected the ECU pipe it fluctuates.  So its deffinatly since that, but because it boosted higher before its possible without the ECU cable, the boost solonoid doesnt work?   I think the boost solonoid is the thing that makes that ticking noise like mad when its ticking over?

If the boost solonoid doesnt work with the ECU pipe off, its possible its gone so long without working its gone wrong or sticky,  if it has been working the whole time, its something else.... If that makes no sence im sorry because i have confused my self