boost gauge needle shaking

[jay-red]

i installed an aftermarket boost gauge, followed the vfaq write up on where to tap the line into. It works, but when at a cold idle or when wot and peak boost the needle shakes, the worst is when you are wot. One thing i noticed was that at idle it shakes with everything else in the car (poly mounts and balance shaft removed) almost as if that is causing it to vibrate, but when WOT it is so bad i can hear the needle shaking in the gauge.

I searched around the net and found many with similar issues (on different forums) and they said that you need a restrictor for the line going to the gauge, or to tap another source. i added a restrictor and it didnt really help. The gauge is securely mounted also.

 

[gofer]

wheres your gauge tapped and does the car shake at WOT when the gauge is dancing?

 

[dsmfa9nutter]

Restrictor on the boost gauge line? I think you misunderstood a post or two. It's possible the gauge you bought is crap, the needle should move smoothly.

 

[jay-red]

I tapped into The Fuel Pressure solenoid just as described in the vfaq write up.

This is one of the threads i read that suggested a restrictor:
Installed boost gauge.. needle vibrates a LOT

The needle moves smoothly under normal acceleration, and i was just watching it and at idle or low rpms when the car shakes a little the gauge seems to shake the exact same way, but at WOT its different. And no the car isnt really shaking at WOT.

 

[MrBoxx]

What BOV do you have? Does it flutter a lot? My line of thinking here is that you're getting a fluttering boost reading due to a fluttering BOV diaphragm.

For a diagnostic, find a buddy with a boost gauge to spare, and install that. See if the needle on the other gauge does the same. If it does, your problem lies in the intake tract. If not, then your boost gauge is to blame.

 

[jay-red]

Im still have the stock 1g BOV, that sounds like a good place to start.

 

[gofer]

if your car idles fine and the boost gauge is dancing around while its idling (vacuum) id do what eric said, change gauges.
in my personal experience with autometer boost gauges don't use the silicon hose because it cracks and causes vacuum/boost leaks, that could be the culprit as well if your running that clear hard plastic line...

 

[jay-red]

if your car idles fine and the boost gauge is dancing around while its idling (vacuum) id do what eric said, change gauges.
in my personal experience with autometer boost gauges don't use the silicon hose because it cracks and causes vacuum/boost leaks, that could be the culprit as well if your running that clear hard plastic line...

At idle it is just a slight vibration, but it matches the vibration of the car perfectly. The worst part is when its WOT. I am using that stock plastic hose that came with the gauge i should check that.

 

[Clinical]

Sounds like it may just be the gauge itself.
Did you buy the gauge new or get it used?

 

[JAXWHITE1G]

Does it shake in vacuume and boost or just under vacuume. If you rule out the gauge being bad and it only shakes in vacuum it sounds like a bad valve. A leaking valve will cause a rough idle but will smooth out while driving if it isn't leaking too much. I would get a vacuum gauge and connect it directly to an intake vacuume port. That should give you a better reading.
Mike

 

[ReYnd]

Go buy six feet of 5/32" vacuum hose. Got mine from Napa, it comes in 6' sections, how convenient. It's the perfect length for routing to the gauge through the speedometer grommet up to the A-pillar, with a little left over for cleaning up the lines around your fuel pressure solenoid. Much better than that crap clear plastic hose that came with my gauge.

Try that with your gauge first, then another gauge if you can get your hands on one. Then check the BOV. And finally, because it's the least amount of fun, do a boost leak test. Maybe there's a chunk of hose flapping around or something obscure like that. One thing's for certain, a restrictor isn't going to help. At best it will cure the symptoms but not the problem.

 

[MrBoxx]

I also recommend changing out the nylon line to a standard rubber vacuum hose. You'll probably need the barbed fitting (nipple style) that adapts the back of the gauge to the vacuum hose. Take the gauge in to the store to help get the correct one.

 

[gofer]

or you can order this from STM... STM - DSM - GAUGES | GAUGE POD | PILLAR | INSTALL KITS

free shipping i think too! scroll down, its the boost gauge install kit. like eric said though, you will need to walk into home depot and get some fittings to get it to adapt to the back of your gauge.

 

[YoungCesar303]

Restrictor on the boost gauge line? I think you misunderstood a post or two. It's possible the gauge you bought is crap, the needle should move smoothly.