boost then fall

[Turbotickler]

1990 Talon TSI AWD-

If I ease on the gas, the boost gauge slightly moves up like it is supposed to; If I press a little more, the gauge goes to full boost and the engine falls on its face.

If I disconnect the MAF sensor the car runs better, not perfect though. I have replaced the sensor with a new one,, but it is no better.

WTF is going on??

can anyone help me?

 

[flytalon93]

What is full boost for you? Full boost for some folks is 21psi and others is 12-15psi. If your full boost is too high, for your setup, then you are probably pulling in some serious knock which will hinder performance.

 

[turboholic]

Originally posted by Turbotickler
If I ease on the gas, the boost gauge slightly moves up like it is supposed to; If I press a little more, the gauge goes to full boost and the engine falls on its face.

-Does the motor start to stumble as soon as the needle on the boost gauge goes from vacuum to pressure? if yes, check for leak on the intake pipe.

 

[TheTSiGuy]

hmmm,

my boost gauge doesnt even move one bit unless my accelerator is fully down the the floor. Then i have to wait till about 3000 rpms for it to start moving. I have a big 16g, so im not sure if that has something to do with it. Am i supposed to be making boost even with 50% or so throttle?

 

[turboholic]

Originally posted by TheTSiGuy
my boost gauge doesnt even move one bit unless my accelerator is fully down the the floor. Then i have to wait till about 3000 rpms for it to start moving.

-If you step on the gas slowly, only the RPM will increase, but if the motor start to have load, the needle will start to move up.

 

[Turbotickler]

-Does the motor start to stumble as soon as the needle on the boost gauge goes from vacuum to pressure? if yes, check for leak on the intake pipe.

- turboholic

yes! as soon as the gauge gets to any pressure, the engine makes a fluttering sound and falls on its face..

why does it run better when the sensor is disconnected?

Ive checked all the vaccum hoses and I am sure you are right.. but I cant find the leak anywhere.

Here I go again..

 

[Turbotickler]

Originally posted by flytalon93
What is full boost for you? Full boost for some folks is 21psi and others is 12-15psi. If your full boost is too high, for your setup, then you are probably pulling in some serious knock which will hinder performance.

thats right.. Im sorry I forgot to mention it.. but I am still all stock.

Havent graduated to the major leagues yet.. but I will.... soon..

 

[LAZPNO]

What are your plugs gapped at?

 

[babell2]

Originally posted by LAZPNO
What are your plugs gapped at?

Thats a good point. Have you replaced your wires lately? Under pressure the Plugs could be cutting out and you would get the same results.

 

[Turbotickler]

Originally posted by babell2
Thats a good point. Have you replaced your wires lately? Under pressure the Plugs could be cutting out and you would get the same results.

yea.. the wires are just a few months old. and my spark plugs are new... the auto parts store claims that they are supposed to be set at .44, but thankfully I have my books and you guys. right now they are set at .28.

 

[LAZPNO]

... What in the hell type of plugs need to be gapped @ .44? What type of plugs do u have in your car? It sounds like a boost leak, blow out, or some other type of spark problem. You said you have a big16, what are you using for fuel modificaiton/control?

 

[Turbotickler]

Originally posted by LAZPNO
... What in the hell type of plugs need to be gapped @ .44? What type of plugs do u have in your car? It sounds like a boost leak, blow out, or some other type of spark problem. You said you have a big16, what are you using for fuel modificaiton/control?

naw, I am still all stock. I had to buy three different set os plugs so this time I just got the cheapest one that I could find. it did the same thing with all the other plugs. now I have some Autolite copper cores. ( dont laugh)

another thing that I just noticed was when I just test drove it. the idle adjustment screw just popped clear out of the hole. what happened?

 

[turboholic]

Originally posted by Turbotickler
- turboholic
yes! as soon as the gauge gets to any pressure, the engine makes a fluttering sound and falls on its face..
why does it run better when the sensor is disconnected?
Ive checked all the vaccum hoses and I am sure you are right.. but I cant find the leak anywhere.

-Get/borrow an air compressor and long air hose(s), remove the intake pipe between the air filter and the turbo, seal off the turbo inlet tight, 2" or 2.5" (depend on turbo inlet dia) and a pipe end cap work well, cap off the turbo with hose clamps, remove the air hose that goes to the brake booster on the intake manifold, SET THE REGULATOR ON THE COMPRESSOR TO ~15PSI, hook up the air hose to the booster air hose, set up the compressor away from the car for less noise, open the throttle plate, listen for leak (main pipes), don't forget to check the intercooler too.

-To test the MAF sensor http://www.geocities.com/MotorCity/Downs/7678/dsmtests.html

 

[TheTSiGuy]

Originally posted by Turbotickler
naw, I am still all stock. I had to buy three different set os plugs so this time I just got the cheapest one that I could find. it did the same thing with all the other plugs. now I have some Autolite copper cores. ( dont laugh)

another thing that I just noticed was when I just test drove it. the idle adjustment screw just popped clear out of the hole. what happened?

looks like you just did the same thing i did. my biss screw was apparently too loose. Popped clear off. Luckily, i found it. Keep it tightened down enough man

 

[Turbotickler]

Originally posted by TheTSiGuy
looks like you just did the same thing i did. my biss screw was apparently too loose. Popped clear off. Luckily, i found it. Keep it tightened down enough man

.. yea.. thankfully I had an extra intake laying around.. I just got the screw out of that one..


turboholic- THANK YOU!!!!!! that is exactly what I needed.. I will go out to the garage and try that in a few!

I will let you know what happenes.