There's a device on the turbo activated by intake manifold vacuum that prevents sudden throttle changes from causing turbo surges. It has a rubber diaphram that starts leaking after a while and produces erratic turbo operation. In the case of my 740 (Mitsu Turbo) it has a really bad leak and causes a severe missing problem whenever the turbo is activated. I took one from a wrecking yard thinking they were all the same but they're not. Mine has about a 1/2 inch section that goes into the turbo housing and this one goes in about 1 3/8 inches. If you need one let me know: lgspooner@adelphia.net You can test it by putting a vacuum pump on the vacuum tube connection. If it holds vacuum it's OK. Or you can push the plunger in w/ a screwdriver and then put your finger on the vacuum hose connection. Release the plunger and you should feel suction at the connection. No suction no good.

Could you describe the severe missing problem you have? I am trying to diagnose a severe hesitation/bucking between 1,500 and 4,000 rpms that only happens under load. It happens when you try to accelerate with any more than a slow, light pressure on the accelerator.

My engine starts missing any time the boost needle gets in the yellow area (to the right of 12 o'clock) indicating the intake manifold now has pressure in stead of vacuum. The quicker I press down on the gas the worse it gets. Can't really use the turbo at all. I've checked all the intake and turbo hoses for leaks, tried higher octane gas and cleaned the injectors and replaced the injector o-rings w/o help. The engine runs great w/o the turbo and I can run it all the way past 4000 rpm witout any problems as long as I do it slowly. Which isn't much fun but I guess it is some benefit because I'm being forced to takes it easy with the gas peddle and it's helping save some money at the pump.

ok lets start the hose u took out of the gunk yard goes to a garet turbo verry common turbo for volvo u have an mitts. the hoses and hook ups are verry differant.i have a mitts. on my 91 940t just rebuilt it my self.the hose gets verry soft from oil gong in to them not good.u need to check your air filter more offten,if your filter gets gloged makes an vacum and the oil goes into your inercooler not good.