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850 Solved. Rough running and less boost 850 turbo

edited November 2019 in Troubleshooting

I went for a night drive last night with the local Volvo club. All was well until the car had a small backfire which actually didn’t sound like the usual backfire you get. It was more like a pop through the exhaust. The car then ran very rough at the lights and stalled. It started back up and ran Okeysh but noticed maybe 10% or so less and anything on the 1000 - 2000 rpm range it was about to die. I limped it home as a result. I automatically though maybe an intake hose or something like it as an issues. Couldn’t locate anything after a quick look so I locked it up overnight. This morning started up and went for a drive and all back to normal like nothing happened. Boost is fine and runs smooth and strong again. I’m lost as to what it might or might have been. Any thoughts? Car is a 850 t5r manual. Full stage 0 done not long ago and has a bsr full car back as the only mod running std boost.


  • jamesincJames @jamesinc Oz Volvo Ice Fortress

    I had similar symptoms once that turned out to be the little hose to the IAC valve having a hole

  • Thanks for that. I’ll get that checked.

  • Had this checked out. Looks like a turbo pipe hose has a split in it. Will get a replacement for it right away.

  • Update on this. The hose didn’t fix it. It ended up being a stuck idle control valve and a faulty temperature sensor. Combination of this was causing it to play havoc. All sorted now and runs like new again.

  • Ex850RSnoopy @Ex850R Somewhere Over the Rainbow. Melbourne.

    Best to do a 'stage 0' on it,everything is going to need done,it's an old car .

    Just about every P80, (850 and S/V 70) needs over $2K spent on it to make it like new and not going to break down at some point.

  • Thanks. I have done a very thorough stage 0 with over $4k spend at my dealer. I guess the only 2 things not done were the icv and the temp sensor. The o2 sensors and all other bits including all hoses, belts, pulleys, gaskets, engine mounts, ignition, and anything else that can affect engine running. all that and more were all done plus suspension bushings and so on. I’m confident this was finally it as now it is spot on and doesn’t even feel like it will play up.

  • Ex850RSnoopy @Ex850R Somewhere Over the Rainbow. Melbourne.

    Wow, dealer!?

    I'm talking $2K worth of parts from USA, cheaper than here.

  • i got all my stuff from fcp. The cost I mentioned was virtually labour involved only but yes definitely worth getting everything sourced prior as it is a lot more cost effective. reason I got my dealer to fit is that they are part of the group I work for and I get internal rates and someone that does a great job.

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