I was having problems with my 91 940t. I couldn't get the car to rev over 5000 rpms. This only happened if I was on the interstate doing 55 or so. I could floor it from a red light and I would go through 1st into second with out bogging down, however if I would keep it to the floor when it would hit the 5000 mark in 2nd it would act as if it was starving for fuel, and buck. The car was also sluggish. I've had the fuel filter changed, fuel pressure test(48-52 lbs) air filter changed, new plugs and wires, had a back pressure test done and it showed I did have back pressure. The gauge went up to the number 2 when the guy reved it to around the 5000 mark.(not sure what the increments of measurement were) Had the CAT changed at midas. Now the car is much more peppier not like it was before all of this, but better. So I drive it on the interstate and it the motor winds out pretty nicely seems to be not as strong as before but much better still. I go to accelerate agian and I hit about 4500 rpms WOT and the car gets weak and dies on the interstate. I try to start it and it barely runs. Finally get the car to run but now I cant get past 4000 rpm WOT it just dies as if its hitting some sorda rev limiter all power stop until I let off the gas. Please somebody give me some sorta direction to go. The car does have turbo+ and it has 151,000 on it!! THanks in advance!!

should have gottan a Volvo cat or a performancew aftermarket, could be a bad O2 sensor too.

Check to see if the foam rubber from inside the air cleaner box is coming loose. It will suck into the screen on the air mass meter and give the symptoms you describe. It is a good plan to take all of the foam rubber out or it will get you sooner or later.
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Leon Ramseur, 1991 940, 1990 760, 1990 740, 1990 745T & 1989 780

Thanks for the advice, already beat you to it LOL. ALthough I just removed the foam thats stuck on the top of the air box. Are you talkin about the yellow foam pad at the bottom of the air box!!

Does the new converter pipe have a plug you can unscrew upstream of the converter itself? If it does unscrew it and see if the performance is any better with it out.

Is it throwing black smoke when it bogs down? If it does check for a leak in the turbo hoses. These can be difficult to find. I made a plug to clamp into the hose that I removed from the turbo and then adapted a Schrader valve so I could pressurize the system with 15 lbs of compressed air and found the leak in the hose that had evaded me prior to that.

Randy

I'll check to see if the new converter has a plug I dont think it does! And I get no smoke what so ever outta the car it just dies!!

I was also wondering is there some sorta way the turbo can "sense" back pressure and stop putting out. It would seem as though this is excatly what's going on. The new CAT is about 1/2 the size of the original, maybe its still restricting??

I just had a power output problem with my 945T, and found the intake port had loosened up from vibration. Totally destroyed performance, and sounded like the turbine was loaded with crap, made a buzzing/whirring sound when I got into boost. tightened the intake connection. and Wha La, purring like a sleeping tiger again.