Possible vacuum leak and weird vacuum/boost readings.

[Rev]

I have a boost gauge hooked up to one of the 3 vacuum ports but I have some weird readings and have done some tests with strange results. On the road, it is very sluggish but at about 3500rpm you can feel it boost. Barney said to me he could never get his boost gauge to work when he had centerpoint injection, but I think there really is a problem because of the results.

Firstly, the boost gauge reads:

0 PSI/Vacuum at idle
As I up the revs to around 3000, it goes to -7 Hg
If I keep revving it up to 5500, it goes back to 0-1 PSI...

Next thing I did was, while the car was running, remove the vacuum line that the boost gauge is plugged into.. with a vacuum leak there now, shouldn't the car idle erratically or go rough or something? Because if I unplug a vacuum line, it makes NO DIFFERENCE at all.. idles and revs the same as when it was plugged.. it's not rough or anything...

I've checked the intake piping and all the clamps are tight, all of the vacuum lines are plugged in, etc.

Any ideas? The turbo is a TC-06 and has some play in it.

[Paradoxx]

try taking off the vacuum hoses and giving them a clean, or even replacing them. the boost gauge wouldnt read anything significant under no load, it should read about 0 when just revving it and about -.6 under idle. does it read correctly under boost (when ur driving it). If you unplug the hose and it doesnt do anything its probably a blocked hose. maybe try using a different hose, one that is closer to the manifold maybe?

Steve

[Chris 83JA]

Does it centre to 0 when the engine is off but the ignition is on?

[hcca]

When I turn the key to ON, mine flicks to the far right.. then it does all sorts of weird shit when the car is started. I know I don't have the lines hooked up right though.

[scum]

boost gauges work best of big lines, like the break booster line or something. my old cordia had some weird import vac lines in it for polution stuff and i found that some worked on a venturi effect. at idle they read nothing but as air speed increases they start to read a vac, then when boost comes on they slowly creep up to +preassure...

my 2 cents.

[Rev]

try taking off the vacuum hoses and giving them a clean, or even replacing them. the boost gauge wouldnt read anything significant under no load, it should read about 0 when just revving it and about -.6 under idle. does it read correctly under boost (when ur driving it).

Ah ok, yeah mine is showing similar figures to those, except no boost. :(
I was under the impression it is supposed to be in big vacuum at idle (12-15).


I'll try connecting the gauge off the map sensor port.. need an adaptor or something though because the gauge has the small vacuum port, but the map sensor is the larger one.

Does it centre to 0 when the engine is off but the ignition is on?

Yeah.. well, it is ever so slightly on the boost side with ignition on but engine off (like 0.5 psi).

boost gauges work best of big lines, like the break booster line or something. my old cordia had some weird import vac lines in it for polution stuff and i found that some worked on a venturi effect. at idle they read nothing but as air speed increases they start to read a vac, then when boost comes on they slowly creep up to +preassure...

Ah cool, I might just have it on the wrong port.. I've tried it on those 3 ones that are next to eachother on the TB, and also on a double-adaptor with the FPR port.. both give the same readings. I'll try it on the map sensor line tomorrow.