boost gauge readings

mint93SC

Registered User
my friend just bought his SC last week, a 94 5-speed, 64,000 miles.

At idle his boost gause reads right around 30 in. vacuum and under full load it might only read 5 psi. I know its boosting but what could effect the gauge? When the car is off the needle rests right aroung 10 in. vacuum.

What can be done to make the gauge read close to where the boost levels really are?

any help is appreciated
 
The guage is definitely off the mark if it is reading 10 in. vacuum when the engine is off. It should be reading zero. You could try removing and repositioning the needle at "0". Not the best fix, but that should give you a reading closer to the 20 in. vac at idle (instead of the 30 in. you are getting now). These guages aren't all that accurate anyway, so the best fix would be a good calibrated aftermarket replacement, if you want a truely accurate reading.
 
thanks guys

I know when idling around 18-20 is normal. Ans i know that he should be getting at least a solid 10psi, but i havent seen the gause go past about 4-5psi.

What would be involved to take the gauge and make it read zero when the car is off? I know the cluster would have to come out most likely, but if anyof you guys can help me, (well my buddy really) i would appreciate it
 
My 93' had the same problem, I decided to simply force the needle back into place "WTF it was driving me nutz" anyhow there seemed to be a splined kind of feel that would allow the needle to move where ever i pushed it.
To make a Long story Short
the needle is operating perfect. :)

You don't need to remove the cluster, Just the clear plastic.
 
Last edited:
Top secret instructions

As much a pita that the 94/95 dash is to remove, i'd just add a new boost gauge in a pilar pod. Then again, havin this myself, I know how innaccurate the factory gauge is. If you need teardown instructions, here they are.

1.remove lower panel (3 8mm bolts on bottom side)
2.remove 4 or 5 phillips screws holding dash on
3.remove 2 7mm bolts or phillips screws under top of dash by cluster
4.lower steering colum (optional - gives you a little more clearance for panel removal)
5.remove the 4 7mm bolts holding in the cluster
6.tilt the cluster bottom up, then unplug the 2 plugs, and 1 vacuum line
7.jiggle cluster out
8.now on a flat surface, remove the 7 5.5mm bolt/torx screws
9.remove plastic cover

Now do what you must, as you should have realized what a pain the 94/95 dash is to remove. Check any and everything. Installation is opposite of teardown. Hope this helps. I just finished putting my dash back in last night. It never gets any easier. Best of luck, Alyn.
 
Billabong089 said:
should read 20-21 vac

My Cougar when first started in the cold morning reads around 16-17 vac and then later on when the engine is more than adiquitly warmed up it sits at like 18-19 vac. Is this normal or is it just an inacurate gauge too? I notice that when the car is off the needle sit just a hair left of 0. Just say that the gauge was acurate what would cause my lower vac #s? A leak?

Thanks!
Shane
 
Hope this helps

My gauge has always sat a hair left of the 0 mark on the vac.boost. gauge. In comparison between the new gauge, the vac is a tad less that on the aftermarket gauge, and the boost on the new gauge is more quicker to the point. The factory gauge runs out at 15 and I'm hittin 17-18 psi with the aftermarket gauge. The aftermarket gauge is more responsive as well.
 
quick35th

The only thing that comes to mind (that might cause the variations in the boost guage when the car is cold and when it has reached operating temp) is the change in the density of the air at different temperatures. There could also be a slight leak at the guage line fittings that "seals itself" as the fittings warm up and expand. Just another one of those little "SC mysteries"...

If you had a significant vacuum leak, you would experience some performance issues, so if everything seems to be running smoothly, I wouldn't worry about the guage too much.
 
LJGriggs, thanks for the reply. I think I will just ignor the gauge since everything is running properly and I will just keep driving the wheels off of the poor gal. The XR7 is about 200 miles from turning 196K and still going. Of corse it helps that I baby it and it rarely sees boost anyways so the gauge thing really doesn't matter much.

Thanks!
Shane
 
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