boost issues..starting to go crazy

**thenofjboy** · 05-06-2008 10:43 AM

i have 98 B5 giac chipped. I usually get around 15psi & everything was fine Friday but when i went to drive Saturday, that was it. I was working on my heat shield friday and was moving the air box around etc. but i checked everything all the tubes and hoses that are attached to the lid of the airbox.
Now i boost to almost 10psi. and its weird when i am in any gear and let off the throttle, the boost reads -25psi. It idles fine at around -19 in the hose pressure. Even when im driven, the gauge reads 0 or below. i have to almost floor it to get it over the 0 degree mark. I used to be able to floor it and hit 15psi no problem.
. I still boost at like 10psi or so I can hear the turbo, it sounds different. I think bc of the possible leak. It sounds like the turbo spinning up ut i think i hear the leak. My pick up is no where close to what it was but i still feel it pull some. So i dont think its the turbo.
Im going to check the DV with my stock one. When i was fooling around with the airbox, i was moving the top of it around and the only thing i unplugged was that wire that goes across the top if the airbox to the N75. I checked the connection and its in.
I might have leak and im going to make that little tool that people talk about on here to test my pressure out. Can turbos run in reverse? It just seems weird that it drops that much when im off the throttle and i cant boost like i used to!! any advice??? thanks in advance

**haus4** · 05-06-2008 10:49 AM

definitely sounds like a boost like. make the gauge to double check. Also look at all your boots and connectors.

the negative boost refers to vacuum your car produces. And your turbo cant run in reverse, or you'll have serious issues.

**Ewok_Fetus** · 05-06-2008 11:00 AM

Check your L hose between your coolant tank and intake manifold... Common problem and will cause what looks like a boost drop on your gauge...

**Kyle H** · 05-06-2008 11:45 AM

Originally Posted by thenofboy

when i am in any gear and let off the throttle, the boost reads -25psi. It idles fine at around -19 in the hose pressure.

Just FYI, when it goes into the negative side your boost gauge will read in InHg not psi.

You problem sounds like a boost leak or wastegate issue to me.

**thenofjboy** · 05-06-2008 12:35 PM

thanks. i didnt think it could run in reverse i just got confused when i saw my gauge show a 25mmhg. im going to check the gauge when i get home. im not that newwww but what do u mean by boots? you mean where the connections are at?

**thenofjboy** · 05-06-2008 12:36 PM

Originally Posted by Ewok_Fetus

Check your L hose between your coolant tank and intake manifold... Common problem and will cause what looks like a boost drop on your gauge...

i checked the EVil L hose and it looks good but i know thats not aways right. i need to get naother person to feel and look at the L when i giv eit gas...

**thenofjboy** · 05-06-2008 12:48 PM

ITS FRUSTRATING!! haha obvioulsy. The gauge isnt reading like it would use to. I really hope its just a boost/vacuum leak. I can still bost some like orginally said but my accelartion is no where close what it used to be.
I gota make that little tool to hook onto the turbo inlet and go from there. i just want boost!! is that too much to ask for haha
thanks in advance

**ct1.8t4me** · 05-06-2008 01:36 PM

Do you have any Check Engine Lights?

Does your exhaust sound muffled at all? It could be a random catalytic converter failure. It happened to me. My cat just crapped out on me one day. The car ran fine one day, then the next, it sounded like someone had stuffed a potato in my exhaust and the car would not boost at all or it took a long long time to build boost. Turned out that catalyst material in the converter had broken free and rotated inside the housing causing a huge blockage.

One test for this would be to take the first O2 sensor out and secure it somewhere out of the way, then take it for a drive. See if it boosts significantly better. If it does, this could be your problem. Don't drive like this for any prolonged time though as the ECU uses the first O2 sensor to calibrate the air/fuel at wide open - you could blow your engine tooling around without that sensor there thinking you are the shit now that your car works again...

**thenofjboy** · 05-07-2008 02:25 PM

Originally Posted by ct1.8t4me

Do you have any Check Engine Lights?

Does your exhaust sound muffled at all? It could be a random catalytic converter failure. It happened to me. My cat just crapped out on me one day. The car ran fine one day, then the next, it sounded like someone had stuffed a potato in my exhaust and the car would not boost at all or it took a long long time to build boost. Turned out that catalyst material in the converter had broken free and rotated inside the housing causing a huge blockage.

One test for this would be to take the first O2 sensor out and secure it somewhere out of the way, then take it for a drive. See if it boosts significantly better. If it does, this could be your problem. Don't drive like this for any prolonged time though as the ECU uses the first O2 sensor to calibrate the air/fuel at wide open - you could blow your engine tooling around without that sensor there thinking you are the shit now that your car works again...

no CEL at all and no weird noises from my exhaust. but im stil goin to take out #1 O2 sensor and give it a try. I think my CAT maybe bad or going bad becuse it was smelling rotten and i read a post on here that said that could mean its done or soon to be.

**thenofjboy** · 05-07-2008 02:29 PM

i saw this on how to check for boost leaks:
http://audizine.com/forum/showthread.php?t=104080
It sounds pretty simple, take off the turbo inlet and connect this new fabricated tool to test it. OR am i connecting this new tool to the rubber turbo inlet hose itself?
Is there anywhere else i can test it, rather than the turbo inlet?
thanks in advance