1988 760 wagon, Turbo only works when it wants, PLEASE HELP!

[88760w]

I just purchased a volvo 760 turbo wagon. It drives like a dream when the turbo is functioning properly, but the turbo doesnt want to work all the time. When I get in and start driving, it takes a while for the turbo to start working. If I start the car and let it warm up for about 5 minutes, the turbo will work within the first mile of driving. The turbo always functions fine once it kicks in, until I turn the vehicle off. It never works right away after starting the vehicle though. The turbo was replaced last year with a used one last year. Does anyone have any suggestions? Thanks!

[Kmaniac in California USA]

First of all, my Volvo is not turbo charged and I know nothing about how a Volvo turbo is arranged. The only turbo charged car I own and have worked on in my 1991 Dodge Shadow.

Now, I am purely speculating, but I think I am on the right track. Most turbo chargers have a device called the wastegate. This device prevents overboosting by letting some or all of the exhaust gases bypass the turbo impeller during normal operation. Most wastegates are engine vacuum operated. I think you may have a malfunctioning wastegate.

Now I also know that some cars have vacuum control devices that are engine coolant temperature controlled, either turning on or shutting off vacuum sources depending on coolant temperature.

My SWAG is that the wrong vacuum line got reconnected to the wastegate and the vacuum to this line is either turned on or shut off when the engine coolant reaches operating temperature, which keeps the wastegate fully open when cold (no turbo charge), then allowing it to partially or fully shut when warm or hot (turbo charge).

Check the operation of the wastegate and any vacuum sources to it. Also verify proper vacuum hose routing. I don't know where you will find a schematic, but I believe this is your problem.

Good luck and let us know what you find.