96 850R cuts out

mtabbert86 · Post by **mtabbert86** » 07 Mar 2011, 11:16

Hey everyone, another Volvo newb here needing a little help and insight. I just bought my first ever Volvo/turbo a few days ago and so far it has been great. So it is a 1996 850 R sedan with about 140k miles. I will be working on it myself as I am an auto tech by trade. I typically work on Land Rover, BMW, and Jaguar though and do not have any experience with Volvo's or turbo's aside from tiny and old Rover diesel turbo's that barely prduce enough boost to help a lawnmower, no electric solenoid wastegate or anything fancy like that. I have done a little research on a bunch of my issues though the two I'm asking about here, I haven't really gotten anywhere on.

Problem #1 is that the engine/turbo cuts out under heavy throttle, usually for no more than a second or two. I can't tell if the turbo is cutting out making it fall flat on its face or if the engine is cutting out causing the turbo to unspool. When it does it, engine power is pretty much instantly gone, then instantly back a second later. Doesn't matter if it is hot or cold. I just put in new Denso Iridium spark plugs the other day, and a new air filter, and changed the oil. Plug wires and dizzy cap look good/newer from the outside but I haven't taken the cap off or checked wire resistance. Any ideas?

Problem #2 regards inoperative seat heaters and inoperative rear defrost/heated mirrors. I have access to factory wiring diagrams but haven't looked at them yet. Underhood fuses are good. Mostly just curious to know if there are specific problem areas in those systems.

Thanks in advance for any help!

850_GLT_Owner · Post by **850_GLT_Owner** » 07 Mar 2011, 17:07

I have a 97 850R, and it sounds like we have the same problem. Does it happen when your turbo boosts up to near full, cuts out pretty harshly(lurching you forward in your seat) and then all seems back to normal? I think that is the fuel cut happening when the engine builds to much pressure from an over boosting turbo. I haven't fixed it yet as the weather has been shitty up in the north east, but i have a hunch that it has to do with the boost control valve that is on the side of the airbox. There are 3 vacuum hoses that connect from that to various spots on that side of the engine.

I believe #16 is the boost control valve/TCV[turbo control valve]/boost control solenoid. That is located on the left side of the airbox(when facing the windshield) and is close to the distributor cap. I'm having this problem and i need to replace all of those hoses.

I've managed through the last few months by being aware of the boost level and not really getting on it to much. Doesn't cut out and as long as i'm careful all seems fine.

Let me know if this works out for you. If i fix it first i'll get back to you with a more certain response.

This might help too.
https://www.matthewsvolvosite.com/forums ... php?t=6941

also this:
http://www.fcpgroton.com
http://www.ipdusa.com

I've exclusively used FCPgroton for about 8 years now, best prices, OEM parts, standard delivery gets to me in less than 24hrs(one state away)

FCPEURO · Post by **FCPEURO** » 07 Mar 2011, 18:29

You are definitely getting boost cut. What you could do to know for sure is to bypass the TCV/BCS and connect the airline from the cold side to the wastegate itself. If all is good, then get your hands on a boost gauge and see what the car is boosting to. If it is over boosting, you probably need to adjust the wastegate. The PO could have bumped it up a few turns, not knowing what he was doing, to get some more boost out of it.

mtabbert86 · Post by **mtabbert86** » 08 Mar 2011, 09:03

Had I was starting to suspect just what you two are talking about and had a closer look last night. Sure enough, there were 2 disconnected vacuum hoses down by the turbo and another one that was is really crappy shape. So I fixed 2 of them but couldn't find where the other plugged in until I saw your posted diagram. It's the green line, it was hanging down over the downpipe so I figured it could have gone just about anywhere. I will get into tonight after work and fix it.

Thanks again.

Post by **jblackburn** » 08 Mar 2011, 09:10

Fuel cut for sure - it is trying to prevent damage to the engine from over-boosting the turbo. It does slam you hard, doesn't it?

Get a good flashlight or work light. On the S70, that goes to the side of the turbo near the intake pipe. On the 850's turbo (a slightly different model), I believe it can only be accessed from under the car. Either way, that one is a real pain to change.

mtabbert86 · Post by **mtabbert86** » 09 Mar 2011, 08:14

Fixing those hoses fixed it. Now the only problem is that I can't spin the tires up to 40mph, haha! Took a grand total of 10 minutes to fix them, that bottom hose wasn't too bad.

850_GLT_Owner · Post by **850_GLT_Owner** » 09 Mar 2011, 12:49

sweet. How does it feel after you fixed it? I still haven't brought my 850r past like, 3300rpms because of the turbo issue. Will probably be fixing it this weekend. Glad it worked out for you.