940 turbo problems?
 

hello folks! so i bought my 1991 volvo 940 turbo (automatic) on craigslist for a whopping 700 dollars. it was a steal, all that needed to be fixed really was the coil springs... which were broke. anyways, when i first had the volvo whenever you WOT around 40-50mph the turbo kicks in and takes off like mad (rpm goes from 2k to 5.5k practically instantly.....

now for maybe the last 3-4 months the car just isnt that same.... the only time it really kicks in now is when im going 20-32mph. and only shoots up to around 4k rpm when going 40-60mph at WOT

is it definitely a turbo problem?

what is wrong with it?

could it be a tranny problem? (ohh god noooo!!!!)

insufficient information to diagnose.

does the turbo gauge on the dashboard show you're getting boost when you lean on the 'go faster' pedal ? my 92 turbo spools up decent boost pretty darn quick even at fairly low RPMs.

i'd start with the usual diagnostics.... check the vacuum lines and air plumbing. my turbo was sucking in the big air duct that went from the mass air flow meter to the turbo intake, the rubber had gone mushy from 20 years of PCV flug. a new hose ($150 hose, I think, ouch) fixed that nicely.

yeah it shows boost on the guage.

its just it only really boosts hard at lower speeds (20-30mph)

and it used to boost hard from (20-60mph)

idk it's hard to explain i guess.

I'm still sort of a car noob are there some guides for all that turbo diagnosing you speak of eh?

vacuum lines and air plumbing is pretty much visual inspection, anything that looks/feels hard or shows signs of cracking should be replaced.

you also could be suffering from lack of fuel flow at higher RPMs, that will cause loss of power, thats somewhat harder to test (you need a fuel pressure gauge with volvo specific rail adapters, something I sure don't have and I got a fair amount of tools for a tinkerer).

what exactly are vacuum lines and what do they do? were are they all located at on the 940?

they are fairly thin (1/4"?) rubber or plastic hoses that go all over the place, originating from the intake manifold. the engine creates a vacuum (lower pressure than normal) in the intake manifold, and this vacuum is used for all sorts of control systems, including the turbo boost modulator, EGR valve (if you have one), as well as stuff like power brakes, air conditioning flap control, etc.