Hello, as I said I'm new here, as well as to Volvo.
I bought a 91, 940 Turbo a year ago. The fuel pump in the tank was bad, so I got it really cheap. The person who had it couldn't figure out the problem got fed up and "gave it away" really cheap.
That said, I did a little looking and found and fixed the problem. Well I have been driving it for a year with this problem-
when I'm driving non-aggressive and the turbo isn't in full boost ( indicated by boost gauge) it seems to be fine. When I floor it and it is boosting it starts to spit and choke. At first I thought it was some sort of govener, it almost feels like that. But here latley I got P***ed of and pulled to the side of the road, turned the car off and sat for about 30 seconds. Started her back up and the problem was gone. Now this doesen't happen all the time, and it doesen't matter if the engine is cold or at running temp. It is the same, when it does it I pull over and restart it then it's fine. Strange hugh? I'm a novice mechanic at best, got a few tools so I can change the radio antenna and I have NEVER owned a turbo. My first thought isplug wires, but wouldn't they "act up" all the time? Or is it just when they have a huge voltage running thru them? I don't know and I'm sure there is a thousand sensors to change, but a few helpfull comments might point me in the right direction.
Thanks in advance
Apeman

 

Maybe the fuel pressure regulator is going bad?

 

How much boost are you hitting at wot?

Sounds like you are hitting fuel cut with that issue, so check the pumps, and fuel filter. Otherwise itcould be an overboosting issue, check the wastegate, vaccume lines.
It could also be a bad maf.

Nick

 

your probably right about the sensor thing, they needing replacment...but perhaps not. definitely open the engine bay door and check things out; vacuum lines, air flow conduits. check out the ballast resistor, rpm sensor, injector grounds, injector seals, radio supression relay (does 940t have?, b230ft, LH2.4 - i guess it would), fuel injection relay. It may be a failing Air-Mass Meter, which is rather pricey. Regarding the ballast resistors, buy some elctronic cleaner and clean the unit up, and the connecors. clean up the injector grounds too. make sure you unplug battery!

long shot also is perhaps clutch disc...but perhaps that's a manual transmission issue only. make sure your exhaust flow is not retarded.

 

Thanks everyone, what it turned out to be was the fuel pump under the driver seat. It must have been failing all along, though it was a new pump it still failed . After I tried another pump she purred like a kitten

Until..... now

Well she still purrs but she is leaking pretty bad. I had my Mechanic change the timing belt and water pump and seals. after that she was dry as a bone for a week. I am at a stand still, I failed the jiggle test and have Positive head pressure. My dad seems to thinks the rings are worn, but I'm not buying it.
At 165K it's not smoking and has plenty of HP! I cleaned the firetrap or pcv or whatever it's called and it's fine (took the vac line of the turbo and poured gumout 2 cans thru with free flow and no build up of liquid, then change filter and oil before I started engine)
But I'm still failing the jiggle test and have a leak. It seems to be emitting from the passenger side of the engine. I suppose the next thing to do is change the turbo seals, but thats not going to change the positive pressure. Anyone have any ideas?

I also put a new valve cover gasket on and new oil filler cap gasket

Also how hard is the turbo job? I am a little concerned I will break something on it because of the extreme heat fatigue the metal around the turbo has.

Thanks!

 

What is the jiggle test? What are you jiggling? Don't forget the air filter. Did wonders for my 1987 740T.

 

Thanks fredbyte. The "Jiggle Test" is the oil filler cap. As the engine is idling, un-screw the cap and let it rest. If it "Jiggles" as opposed to being "sucked down" you have positive head pressure. If there is a vacuum present it will try and seal.
The first thing I replaced was the filter, I cleaned the throttle body with brake cleaner and used my shop vac to vac out the breather box as well.


I'm leaning toward that firetrap reference, on a turbo it's supposed to be firetrap free, so I am not sure what to call it. The car doesn't smoke at all. Under load at idle or under turbine boost, it remains smoke free. The gas mileage has remained constant as well, around 23MPG highway (LOVE THIS CAR )

Thanks to anyone who wants to jump in

 

VolvoDriver, thanks as well. It's an automatic. And thanks to this board I replaced my overdrive relay and now have overdrive. Thank you all.