Shaky vacuum at idle

[DiamondStarM]

Like the title says, my vacuum used to hold nice and steady at around 19 now if I sit at an idle, after about 10-15 seconds the needle wil start to bounce back and forth quickly between 20 and 15. If I blip the throttle it will steady out for a few seconds then start to shake again. While driving at a steady speed the needle does not shake at all. Any ideas?

 

[DiamondStarM]

I dont know if this is part of the problem or just a helpful bit of information to help diagnose but I cant get a solid tune anymore. Once I get the low trims set right, 3 minutes later it changes +/- about 5 on the loger for the fuel trims. Previously the tune was perfect and would always check with no major shift in the fuel trims.

 

[GVR4592]

Boost leak test first http://www.vfaq.com./mods/ICtester.html

Does it have a rough idle? Also check for leaks between the maf sensor and the turbo.

 

[skinnyt]

you got a vac leak some were,probley were you done some work with the vac lines

 

[DiamondStarM]

I just did a BLT not too long ago, but I suppose its the proper first step to take, thanks for the advise. I actually wasn't working on anything recently. I got the tune perfect and decided to just drive and enjoy it for a while. I did have a misfire because of bad plug wires, but thats just maintenance. Ill report back after I do the test this weekend.

 

[andymoraitis]

Spary some carb and choke cleaner around your vacuum lines with the motor at idle. If the idle changes, you have a leak in that spot. Other than that, verify that gauge actually sits on zero when the car is off. If it doesn't, you likely need a new gauge.

Let us know what you find,

Andy