View Full Version : Vacuum low?

12-24-2005, 12:24 PM
My vacuum at idle is around 16 In/Hg (very consistant), and in gear it drops to around 12. This is lower than what it should be, although not a lot lower. Also, when in gear with the brake on, I thought it's supposed to increase vacuum. The car seems to be boosting fine and the car acts fine. No CEL's. Do you think I have a small vacuum leak starting?

12-24-2005, 01:01 PM
what does your guage read with the car off?

sometimes guages seem to lose their zero...

12-24-2005, 01:28 PM
your vacuume should be negative

12-24-2005, 07:01 PM
SeanF: It's zero with the car off. That part is okay. Actually if anything it sits at 1 In/Hg when the car is off. That said, now I'm only at 15 In/Hg at idle.

Poopie: I'm going to go with: "What?" and then "Thanks."

12-24-2005, 07:36 PM
every time I hear this issue, I offer the suggestion that it may be the 710N starting to go. My 710A was the cause of a small boost leak. It read 15 in of merc at idle and when I replaced it with a 710N, the problem was instantly solved. Only thing was that my car woldn't boost past 8psi and yours seems to be boosting fine. just my .02.

12-24-2005, 10:04 PM
As I've been working on the car I've been replacing vacuum hoses. The DV line is new and the FPR line is new. I'm thinking I should just change the rest of them too.

I installed a new 710N in August when I installed my K04. It shouldn't be that, but I'll have to check everything I guess.

12-24-2005, 10:05 PM
What if you turn the climate control off? Make sure all accesories are off (lights, climate control etc). The more load that's on the engine the more air (and fuel) the engine needs to keep running and the lower the vacuum reading will be. When my climate control, lights and all that are on, I pull about 15-17 inHg, but I've seen as low as 13. If I shut all the doodads off I see about 18-20. Under full engine braking it gets down to 23-24 inHg.

12-24-2005, 10:17 PM
nramsey: I'll check that tomorrow. I too see about 24 (or more) In/Hg when decelerating.

12-25-2005, 02:33 PM
ive had similar problems but my boost guage ended up breaking so i dont know happened
waiting for a replacement