loosing boost

[beagle113]

I just recently bought an 86 944 turbo and everything ran fine. now the boost comes in later than usual and goes away really fast. the more i push the gas pedal, the quicker the boost goes away and it is different in each gear. Does anyone know what i should look for to fix this problem?

[ae1969]

I am assuming this car is stock....

If you are not having any other major driveability issues.....

I would look at the cyclic valve cracked/vacuum leak. Check all your vacuum hoses......

[beagle113]

it is supposed to have autothority chips but i havent looked yet.

[beagle113]

Well, i just finished checking the cycling valve and it is broke. one of the hose connection posts is completely gone and the hose is just flopping. thanks for your help.

[ae1969]

No problem...

Don't bother replacing it....

This is the time to go to a manual boost controller......

[beagle113]

how do i route the hoses for a manual boost controller?

[beagle113]

i have seen the accuboost controller but from the way it says to hook it up, i would still need to replace my cycling valce because the hose that the controller would be hooked up to is the one that is broke on my cycling valve.

[ae1969]

All you need is a regulator valve in between the hose coming from the banjo bolt (signal) to the wastegate..... you can get rid off all the rest... ( I will look for the vacuum hose layout when I get home and post it)

Your next investment is some chips/wastegate shims/and set the boost at 15.... and you will have a completely new car.

Check with www.gururacing.net

[beagle113]

ok, thanks.

[beagle113]

i installed a manual boost controller and it did affect my car, but not in the way it is supposed to. i when i adjust it for more boost, i still have the same problem of getting boost late and then dropping off really quick. if i lower the the boost pressure, the bar meter gets to about 1.1 and stops. what else could be the problem. how soon should the boost be kicking in? should i hear a noise when the boost goes away?

[ae1969]

Ok first thing if this car is stock dont go crazy raising the boost..... or you will be blowing the headgasket.......

Quite a few reasons that will cause boost drop off. Small intake leaks on the pressure side of the turbo, including all hoses and vacuum lines. Exhaust leaks between the head and turbo is also a problem. Check your turbo to make sure the turbines are not damaged. Weak wastegate spring as well, one of the reasons wastegates are shimmed.....

So:

- see if you can borrow an aftermarket boost guage.... it is difficult to determine what boost you are running with the stock guage. You can easily t- a vaccum line in to the car to hook up a guage...

- Check the turbo.... take a good look at the compressor fins and that it turns easily and is not damaged.

- Check all your vacuum lines and pressure lines.

- Check your exhaust (headers, croosover pipe) for leaks.

If all else checks out then your wastegate is on its way out..

[beagle113]

ok, thanks. i already have the intake off to check all of the hoses and stuff. one more thing, the car seems to stay on boost longer when it isnt warm from a long drive. i will check for exhaust leaks tomorrow.

[beagle113]

in removing the intake, i found a hose that goes over to the brake booster that was broke. i might have caused it to break during the intake removal but would this have caused a leak in the boost? and a few of the 3 prong hose connectors were also broke.

[ae1969]

.... good time to replace all your vacuum hoses and check all the fittings...

Also a good time to simplify the octopus underneath the intake.....

[Lawrence Coppari]

The vacuum leaks will cause you to lose boost. The line that goes to the top of the recirculating valve (near the coolant reservoir) can be the culprit. Your car will not hold boost if the line comes off the valve. Mine came off once. Not much boost when that happens. This tells me the line carries positive pressure when at boost. That helps hold the valve closed. When you let up on the throttle, it goes to vacuum and the valve opens. Your fuel pressure is also controlled by vacuum lines so it is important to have the vacuum system in good shape else you can damage you engine by too lean a mixture. Like ae1969 said, replace all the lines and 'Y' connections.

[beagle113]

i replaced the hoses and connectors and i now have boost. i got rid of the cycling valve and added the manual boost controller.

[ae1969]

Good to hear....

[Lawrence Coppari]

Happy days are here again.

[beagle113]

well, my boost problems were not solved. after i said they were fixed, i discovered more leaks. it was from the throtle body. i bought one and installed it but i still had some lag that i thought should not be there and i looked for more leaks and found them, under the intake. so i replaced all of the hoses and there are no more leaks but when i drive it hard, the car acts like it is hitting the rev limiter but it is about 1000-1500 rpm lower that the rev setting and it still has lag. the car acts different at different throttle positions. what could this be?

[ae1969]

does it happen only under load ? or just sitting in neutral as well......