Volvo 850R Boost issue

iim1awh779 · Post by **iim1awh779** » 26 Nov 2018, 17:48

Long time lurker, great sight have been out of Volvo's for years but when my son needed a first car and I came across a great deal on a pair of 850R's I figured it was a sign. We have been slowly taking the best of both cars and making one nice one.

The issue I am having with the the one we are making the daily driver is boost related. Every time when i start it up and head off to work I have full boost and every thing is working as it should, the issue happens when you drive for 10-15 min at freeway speed the boost goes away and I am only ready 3-4 lbs on the gauge and the car feels like its really down on power. If i turn the ignition on and off then full boost is restored for another 10-15 min. I do not notice the loss of boost when we driving around town as of yet but 10-15 min at a constant speed around town is near impossible.

I have to date replaced all the lines with silicon hose and replaced the BCV as well.

This one seems a bit odd to me and a search of the forums did not uncover any thing that pointed me to any possible cause.

Thanks in advance for your assistance

Andy

Post by **RickHaleParker** » 26 Nov 2018, 18:44

One at a time , try swamping out the Boost Pressure Sensor (8) and the MAF sensor (9).

TP sensor (8)
MAF sensor (9)
RPM sensor (10)

: 850Boost.gif (19.8 KiB) Viewed 756 times

iim1awh779 · Post by **iim1awh779** » 26 Nov 2018, 22:15

Thank you for the advice, i will give it a go this weekend and saw what I can uncover

Andy

Sommerfeldt · Post by **Sommerfeldt** » 27 Nov 2018, 02:09

Since it occurs after 10-15 minutes, it sounds like a short term fuel trim issue. So I'd probably try unplugging the MAF and see what that does, before anything else. It could also be you O2-sensor... but that would normally take longer than 10-15 minutes to have an impact, and you can't just unplug that and see what happens.

- S