Quote:
Originally Posted by davebb
what is the reading of the MAP sensor with the engine not running also show with the atmospheric pressure in vida, they should be very close if all is ok,
Dave
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Good point. It was within 1 digit of the atmospheric reading when I checked that last week.
It's looking like the issue has to be VNT, when under load and anything but HOT.
As my graphs in previous posts show, there is an over-boost issue when it goes into limp, and not when it doesn't.
I can re-produce this at will after a few foot-on-floor > limp cycles. This will cause the turbo to get hotter each time.
I can't see how a fuel issue (eg restricted fuel filter, bad injector etc) can cause an over-boost issue, which goes away when hot. But a worn / sticking VNT when under load could.
The engine is smooth, with no smoke and excellent MPG.
I found this interesting article:
https://www.picoauto.com/library/cas...essure-control
Which says: "have found that in each case the VNT mechanism was more prone to failing at cool engine temperatures. Once the turbo had been worked several times the fault occurrence became infrequent"
I've ordered the turbo gaskets from Volvo and will swap over to the spare turbo I have this weekend if dry, to see if it improves things.