turbo won't spool like it used to
Hello. This is my first time asking a question that has me stumped. I own a 91 780 that ran like a champ and it started to idle up without warning at times. Other times it is fine. While driving it the last time the turbo stop making boost and it felt like my brake booster died. Any ideas as to what it can be. Thanks for any assistance. I also own a 88 740 turbo, 89 740GL, 90 740GL, 01 XC70.

I would pull the intake hose and check for play etc. Waste gate arm could have fallen off. Or intake hose collapsing. Check FAQs..
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Thank you. I will try that.

I just went through this ordeal. Check all intake hoses for breaks, splits and and cracks. I found a split underneath my intercooler to throttle hose that was hidden by the egde of the hose clamp. Pulled the turbo hose off the exit side of the turbo and found it had delaminated inside. After changing these hoses the car still ran with little boost and idle poorly. Keep hearing a hissing type, Psst, noise. So I used a lenght of vacuum hose and found the intake gasket had failed. While removing the intake for gasket replacement I found a split on the seam of the Idle control valve hose going to the intake. I learn how important for the turbo intake system is to being completely sealed. Besides starting out with a clogged fuel filter I thought my richness and excessive fuel consumption was due to the injection sytem fault. With leaking intake systems, the O2 sensor tries to richen the parameters of it's set running range. With everything tighten up and sealed my 89/740 wagon is like the car should be. CHECK ALL HOSES.