90WhiteVrt

i was working on my car yesterday with Poor_old_redneck and found that I have a leak. You can hear multiple air sucking sounds when you start the car that last about a second and then when you run the car wide open, the sounds come back. It's causing hesitation when accelerating in 3rd gear for some reason and poor gas mileage. My Q is, what seals should I check? I was told to spray some either around the intake manifold to check for leaks, but i'm not sure what seals exist around there that would need to be replaced other than the main upper and lower intake manifold. Thanks in advance.

poor_red_neck

Paul,

Starting at the lower intake manifold... you have the metal gasket between the LIM and the block. On the LIM, you have the air control valve (between the 5/6 port actuators)
Then you have the gasket between the lower and upper/exten intake manifold (VDI manifold). On the VDI manifold is the small gasket for the BAC (bypass air control valve).

Then there is the gasket between the upper manifold and the dynamic chamber.
From there is the black throttle body "block" gasket thing. I could never find those gaskets at a parts store, maybe at the dealership... I just used high temp silicone. The orange stuff. Worked great.

Here's a link the FSM for fuel and emissions... just take a peak through that.

http://www.teamfc3s.org/main/factory..._non_turbo.pdf

I ordered all my gaskets from Al smith buick dodge mazda (which is now southern states I think) Right off of wake forest rd. When you get off 440, make a right its 1/4 down on the right.

poor_red_neck

Here's some pics....

My5ABaby

iTrader: (7)

I'd say it's more likely that one of your vacuum lines is broken/punctured.

Btw, how does it idle?

90WhiteVrt

Idle is fine. I have all silicone hoses that are approximately 2 yrs old, so i dont think its them. The leak is most noticeable when you start the car or push it hard. It kind of souds like air escaping slowly out of something, but loudly.

poor_red_neck

Yeah, I've rode in his car, there is NO WAY a vacuum hose makes that much noise.

My first guess was the K/N cone filter, because they are a bit noisy, but this was a very strange noise, I'm about 75 percent sure its not the filter. All hoses are fine, but the strange thing is that it doesn't knock. You would expect a big leak in the manifolds would cause it to run lean and possibly detonate. Then again, the n/a does run rich to begin with. It seems to only make alot of noise when you get on it. It doesn't idle high (except of course for the AWS) and doesn't make sucking noises at cruising throttle... only above about 4K and when you're really on it. It doesn't really hesitate that much but there is a little bit of a drop in power right above peak torque. His secondaries are definitely kicking in as well as the 5/6 ports. You can feel the power start to increase when VDI kicks in (5500???)

We gave it a good look over, and tried to listen for a sucking noise indicating a hose. Couldn't find it. I'm used to looking at an engine without a rat's nest, so seeing all those hoses is quite dizzying. He came over to get his TPS adjusted, and while I was there, we went ahead and connected the 02 sensor. It hasn't been connected for a while, resuling in a code being thrown. So I ran a new wire for the 02 sensor, tested to ensure it was working properly with a digital multimeter. Works fine. I calibrated the TPS first by the "Two LED" method mentioned in the FSM, then "fine tuning" it by the multimeter. The low range TPS is in perfect reading at idle, and sweeps very smoothly. The hing range TPS I could not get below 1.2K ohms however it sweeps to 5K perfectly, and the FSM mentions something about a "self learning" system... I just assumed since the ECU might ignore the high range at low throttle anyways, or else it wouldn't have a low range TPS

Paul...

I have a vacuum gauge laying around somewhere, if I find it I'll let you know and we can just do an idle vacuum test. I need to browse the FSM to see what the spec is for that.

Any other ideas/comments are welcome. I'm a bit rusty, been about 2 years since I've worked on/had my GTU

90WhiteVrt

I went to the dealer to purchase the gasket kit and ran into a problem. My car has an S4 block w/ all S5 externals, so I wasnt sure if I should get the S4 or S5 gaskets? If there's anyone who's built a motor like this, i'd really appreciate your input. Thanks

90WhiteVrt

a little help

jkimbro

iTrader: (3)

Well, if you're buying gaskets that bolt up to the s4 block, it'd be s4 gasket there...

if you're buying the lower to upper intake manifold gasket, and they're both s5....it'd be an s5 gasket there.