I have no boost on my 88 760 turbo. I was trying to adjust for a knocking noise and now I have messed it all up. I hear a swooshing loud vacuum noise from inside the car, but my boost wont go past the middle and i cant drive it over 40 mph. I put everything back to its original adjustment but it still keeps messing up. it will run fine in the driveway and i can rev it to 8000 rpm but when im driving it feels like something is holding me back and i hear the swooshing of air from inside the car....

any ideas??

 

I would go back and check everything. Maybe you have vacuum leak?
It dosen't sound like it is hookedup like it should.

What exactly where you messing with,and what do you have to make it rev to 8000rpm?

 

well, when i got the car it didnt knock. you could hear the turbo whine but the gague stayed in the middle. so, my thinking was that it was disconnected...and it was. there was a vac t behind the coil and when i hooked it up the gague started working. everything was good. then i had a problem where it wouldnt start, or it would start and die after a few minutes. so, i replaed all the vacuum lines i could find and adjusted the maf sensor screw, air fuel screw, turbo vacuum thing, radio supression relay, ecm, power stage, fuel relay, and finally the distributor. the hall effect inside was medded up. so, now that it wasrunning again, all the adjustments i made wouldnt let the car drive or idle. so i tried to put them back the best i could. it ran good, but knocked. I have been driving it this way for months and its getting @22 mpg.
so, yesterday i had a guy wanting to buy it and i was trying to get the knock quiet, and i took the vac t off the gague again, still nothing, took the vacline off the adjustable thing on the turbo, still nothing, adjusted the screw and nut on the vac thing on the turbo, all thway up and down, still nothing, and the maf sensor. the screw inside spins and spins but doesent stop in either direction. i think thats where my problem is......but im not sure and dont want to throw hundreds of dollars at it just to sell it....if it stopped knocking i would probably keep it..
i dont know if there is a relation between another problem and this but, if i have the a/c on and accellerate, i can hear the blowing but no air comes from the vents untill i let off the gas, just like yesterday... i try to go and i hear the air swooshing somewhere in the dash but go slow.
i get good exhaust from the tail pipe so i dont think the cat is plugged but maybe?
yesterday when i was pushing it hard i noticed black smoke for the first time...
maybe my maf sensor is way out of adjustment? i unplugged it and it will still run, just about the same as if its plugged in, except it idles a little rougher

the boost gague wont go into the white, and it has good power untill it gets there but as soon as it does, it bogs right down....

please help

 

What kind of gas are you running? If you aren't running 91 now, try running that and see what happens.
There is a plug on the downpipe near the cat. Take off the plug, drive around, and see if it boosts better. If it does then you mighthave a clogged cat.
You did do a lot of adjusting.....The AMM might be a problem. Try and clean it.
If the cleaing dosen't work, then go see if you can try a friends, or go to a junkyard and get one.

 

im running 93, thats all i run... ill look for the plug by the cat... what is the amm? air mass mater?

 

Yes AMM is air mass meter (MAF= mass air flow meter) samething. See if you can try another one in your car.
93 is good, so that means something else was causing the knocking.
Another thing you can do...is hook up an after market gauge to see if it is boosting proper(should be between 5-7psi stock).
The vacuum hose in the car will work...it should be under neath the steering column.

What stinks is that the car is a 88...if it was a 89- it would have OBD1 to pull codes (unless I am mistaken and your car has the little box on the drive strut mount to pull codes).

Edit: anyone with a 760turbo and have had this problem is welcome to jump in.

 

do you think that if the vacuum hose from the t to the gague was bad, it would cause such a bigloss of power? i guess what im asking is, when i went looking for the t behind the coil, i traced the vacuum line from the drivers rear engine compartment to the coil and pulled the line. it felt brittle. but didnt break. also, i noticed that there is a 90 degree brass fitting just below the wastegate (i think) (the thing ive been adjusting on the turbo. it has a flat screw and 10mm nut) and the line was broken there. i re connected it but its not real long and it goes down under the car. (i dont know what its for) i would like to replace it also, but i havent had the chance to trace it. i am assuming its not an oil line because is has a vacuum style clamp. im thinking it might be disconnected or broken, somewhere i cant see.

also would volvo run vacuum lines or turbo boost stuff behind the firewall inside the car? seriously, the swooshing noise sounds like its inside the car?

 

AH...that sounds like the problem.

The gauge hose going into the car might be bad and that could be why you are hearing the turbo.
It might have a leak or too.

Take apart the lower dash and check the vacuum line. Reaplace the hoses you metioned for they might be leaking also.

If it is not that then it is some where else.

Edit: can you take a good pic of the turbo setup.

 

ok, ive had a chance to look and play a little more. the boost gauge is not the problem. the line from the gague comes to a t behind the coil. one end goes to the intake, the other to the radio supression relay....is that right?
i disconnected the gauge and capped off the vacuum. still no difference. I had a used maf that i put on from another car but is isnt adjustable. and the car runs but wont go at all, it falls flat on its face.
i took some spray air and fuel intake cleaner and tried to clean out my old one. after re install, it is still doint the same thing. it doesent matter how i adjust the screw, it doesent tighten or loosen, just spins. and nothing happens with the cars performance either way.
i did have the courage to take it out on the street to see if i could "blow" it out.
at the begining it had tons of power, enough to thow you back in the seat, then it just drops off before it shifts. and if i feather the gas, i can get it up to about 50, but if i hold consistant preasure the gas, i lose power. i cant hold the power, and i hear the swooshing.

here is what im thinking, ever since ive owned the car, when it gets up to temp, i hear a pop from the exhaust. it had a new cat back system put on just before i got it. when i investigated it i found a small dent in the rear muffler. i was assuming the metal was just expanding or contracting because of the heat.

how do I know without taking the whole exhaust system off if my converter is plugged? exerything it welded and i would hate to start hacking into it. i did notice that the front pipe and cat back are nice stainless pipe, but the converter looks dark. like somebody replaces everything except the cat. when i tap on it, it doesnt sound hollow.....

another question i have is... if i cut it off and hollow it out, will that affect the turbo preasure?

i did that to an old firebird but it was a regular motor with no turboand i found it actually had more power but the exhaust was louder.....

 

You can hollow out the cat no problem.

Are you 100% sure all the intercooler hoses are good and not leaking?

Is the turbo locked up now?

Did you remove the hose and try spinning the turbo?

 

ok, the intercooler hoses are in good shape, and when i rev the engine they "swell". i replaces the line that connects the waste gate with the thing on top that i adjusted. am i suppose to be ablr to manualy adjust the waste gate fron under the car? because i couldnt.

i did notice yesterday that when i took off the hose to get the air filter top out, that there was oil (a little) inside the hose and where it connects to the intercooler... could a the intercooler be plugged?? and if so, would is cause this type of problem??


turbo is fine, amd spins free. its builging up preassure " or it feels like it does" but just "holds" it. it feels like it wont release it.

i am getting exhust from the tail pipe, but i can block it off with my hand......i also noticed that, if i let it idle and knock....(previous continuing problem) and cover the tail pipe, the knock gets louder, so my thought was if i hollowed out the converter and ler it breathe maybe the knock would go away too? less back preasure?

let me know

 

The Cat might be clogged.
Also make sure that none of the intercooler hoses are collapsing under boost cutting off pressure.

There should also be a drain plug on the bottom of the intercooler do drain the oil build up.

 

I don't think the stock 760 turbo had a brass fitting off the wastegate. It sounds like the previous owner put a MBC (manual boost controller) to run more boost. That could be why you feel it build boost but won't release the pressure.
Dose it look like this?

 

tipsp,

i will take a pic in the morning, it doesent look like that. it is like a 1/2 tall brass can with a flat screw adjustment and a 10mm lock nut. the vacuum line attaches to it and over to the intake.

tech,
i will look for the intercooler plug, and i have an appointment with the local garage to replace the converter. i will keep you updated....

 

ok, just wanted to try the oil in the intercooler thing before i took it to the muffler shop. i took the plug out, and no oil came out. i tried to run it with out the plug, thinking maybe oil might push out or run out faster because of the air, but nothing.

i havent run the car in about 2 days and its really cold this morning. i can see the exhaust fron the tail pipe, so, if my converter or muffler was plugged do you think i would see exhaust?

 

You would see some but you need to see how much flow is coming out.

If you cover the end of the pipe after a few seconds it should blow your hand off. That is unless you have a leak somewhere.

 

ok, here is the verdict.

i just had the cat and muffler replaced. no difference. it wants to go, but just holds back, no boost, and blows black smoke. black smoke is telling me its to rich. so i think it needs air......so i am going to call around and see if i cant find an air mass meter used.

i really dont want to throw any more money at this car.....i mean kbb says its worth 1600, and i know i have at least 2000 in it......and im never going to get more than 1000 for it anyways......

what else?

 

Way to rich could be MAF,O2 sensor,fuel pressure regulator.

 

ok,

went to the bone yard and found 2 maf sensors. one from a 93 960 non turbo and one from a 88 740.....the problem is they are from different models.....and the connections are bigger so, i am going to have to get some hose adapters or something to try and make them work.

will they work?

i also got a fuel preassue regolator from a 87 240 2.3 non turbo...

so, basicly if i leave the original maf unpluged it idles rough and has spurts of power under acceleration but if i leave it pluged in i have no power and blow black smoke....

i also found an aftermarket universal air intake with a cone filter and flex hose. i was thinking of replacing the air box....what do you think?

 

K..It sounds like the MAF is bad.

I would try and run the same MAF, but you should be able to use the bigger ones.

Aftermarket intakes are nice...I bought a cone filter and some pipes from AutoZone for $50 bucks and made my own heatsheild.