mewantkouki

Lately my car has been giving weird vacuum readings on idle. I've got a garrett boost gauge that reads in "inches of mercury" (in Hg). About three weeks ago it was reading about 17 inches of mercury on idle, then the next week it started reading around 15 inches of mercury on idle, yesterday it dropped to about 9-10 on idle, and today it hit around 4-5 inches of mercury. The car boosts fine, it doesn't smoke at all and gets minuscule amounts of blow-by. I was wondering if anyone had any ideas as to why I am losing vacuum pressure on idle. Could it have something to do with the recent temperature change? The car idles rock solid, and doesn't miss at all.

asia989

its a ka i told you this lol

vertigo

check for vacuum / boost leaks

mewantkouki

Got scared and did a compression test #1,200 #2,195 #3,195 #4,195 so that seems ok...
No vacuum leaks, going to pressure test my intercooler pipes tomorrow. wtf?

vertigo

un-metered air will cause a lean condition, as well as too much timing advance which will require more air / less vacuum to idle the engine.

mewantkouki

^ rom tune should have handled timing etc. I'm recirculating the bov after the maf so where would un-metered air come from?

vertigo

The unmetered air could be coming from a vac or boost leak... and a rom tune cant fix that...