Ok My boost guage is not WORKING . I have no idea why it doesn't. All the rest of my guages work so thats why i think that it is just the boost sensor or a bad connection. So i would like to know where the actual sensor is located at. Oh by the way its the stock guage.

 

on the passengers side fender near the air filter box

 

what does it look like?

 

its attached to the front of the pass. side front strut tower. Its a little black "box". It has a wiring harness coming out of the bottom. Are you putting in an FCD?

 

my boost guage isn't working

 

This could be a bad sign. The pressure sensor is also used to tell the ECU how much you're boosting, and alters ignition timing accordingly. If it's a problem with the gauge, just replace it with an aftermarket one as the stock one's not worth fixing. If it's the sensor, get it fixed ASAP, as you risk engine damage running at full load like that. If you haven't found it yet, it's bolted to the front side of the RHS strut tower and has "pressure sensor" written on it. It has one 4-pin plug and one vac hose, both on the bottom.

 

hmm if that sensor was bad, would the thing idle like crap? Or would that be low compression cause my car won't hot start either. When i try to hold an rpm below 4k the rpms bounce up and down. but when i drive the car it drives great

 

hm...
mine isn't working that well either...like one day it works....while another day it doesn't work...but most of the time...it doesn't work.

my car idles fine, and everything seems fine..cept my coolant leak i had earlier...found out its a hose that ripped, could that be related to my boost gauge not working either?

hat to take apart my intercooler to reach the hose..

Yivan

 

NZConvertible is correct! Fix this ASAP! I had the same problem with mine. I tested it by using the shop manuals procedure of applying vacume and the checking the voltages on the connector. Just don't forget to compensate for altitude.

 

does yours go from -20 when key's turned off up to 0 when the key is on? Mine goes right to 0 when the key is turned on, and doesn't go below 0, or above 0.

Oh yeah, and what's +4500 mm mercury in psi?

 

760mm HG = 1 atm = 14.7psi

 

Bookmark this site: http://www.anver.com/document/compan.../pressure.html I think you meant 400 mm/hg. Maybe you didn't. My gauge shows a high of 40 x 10 mm/hg or 7.735 psi.

 

S5 boost gauges go to 450mmHg = 8.7psi

 

oh.. yeah I think that's right.. anyhow.. still working on the problem

 

i thought if u uplug the vac lines going to the boost sensor the turbos will only boost to 5 psi or so.

 

That may be the case on the S5 (witch has ECU-controlled boost, sort of), but not on the S4. What it will definitely do is make the ECU thinks there's no boost, so it won't retard the ignition when you do boost. Tink, tink, tink, boom...

 

Ok, here's a somewhat related question... I have a Greddy FCD that i'm in the process of installing (i didn't get the instructions). I found my boost pressure sensor, but it seems that i only have 3 wires (instead of four). I have a Greddy Boost gauge, but i'm not sure if that's relevant. If anyone has any idea why i'm missing a wire it would be much appreciated

*edit*
Forgot to mention that I have a '90 TII...

 

my pressure sensor only has 3 wires on it too, not 4.