boost gauge question??

[SamSTI]

hi guys!! i got in to my car tonight and the boost gauge which normally reads -0.8 when idle was reading -0.4, the car and gauge is boosting fine and i checked the pipework on the boost gauge, all seemed ok.
any ideas what could cause this??

also i heard a pop from the exhaust on the way home, not sure if linked or not.

thanks sam

[andy-m]

i would guess a leak somewhere between the turbo and the manifold, probably on one of the small vac lines

if it normaly reads -0.8 (As does mine) then to read -0.4 either the turbo would be boosting, which it can't be cuz you are idling, or theres a leak allowing air in.

[SamSTI]

ok mate thanks for the reply, ill have a check tomorrow for any leaks

[andy-m]

i double checked this morning, mine is on zero at idle, the -0.8 reading is when I am accellerating so i'm a bit confused.

[SamSTI]

lol no worries mate, i checked all the pipes i could see this morning, no sign of any leaks, if i did have a vacuum leak somewhere would it cause damage to the engine if i left it?? as car is running fine?

[asperformance]

at idel you will always have a NEGATIVE reading and on throttle it will read POSITIVE pressure.......

anything other than this is a damaged gauge/incorrectly piped/etc??

just to add some gauges only read from 0+ so dont have a negative show on idle

[andy-m]

when you put your foot down, it's negative pressure initialy untill your revs get up a bit and the turbo spools.
mine does read 0 at idle as above so that may be why.

If it is a vac leak, in theory your getting air in which hasnt passed the MAF so fuel mix will be a bit lean. how much leaner than normal though and if it's enough to cause damage, I havent a clue.

[SamSTI]

after having another look this afternoon being mr paranoid lol, i did find a pipe which was sort of half on, seemed to have done the trick

thanks for helping folks
sam