mk3aba20vt

Hi, Im having a few slight issues with my s4. This doesnt happen all the time but sometime going thru the gears under load and kind of getting on the throttle the car will hard cut at around 3500-4k rpm... any idea? and also my boost gauge is reading around -10hg vacuum... i know this is low but dont know what it should sit at at normal idle. ive searched and couldn't find anything on it. Also what would be the causes of such a low vacuum reading. I was thinking maybe timing was maybe slightly off by a tooth, dv valve not seating right. any ideas to look for would be much appriciated so i can try to track down these issuses. when i take the foot off the throttle when driving the vacuum goes up to around -20 to -21 area.

UrS4boy

Your vacuum is normal(ish). Typically 10 inches of mercury (Hg) vacuum on cold start-up idle. As the engine warms, this goes to about -14"Hg at idle. -21"Hg on full throttle lift while driving is what I get too.

The hard cut could be a boost leak (e.g. split in the Michelin Man hose between the cross over tube and the inlet to the OE intercooler) but it could also be a bad mass airflow (MAF) sensor connection. Unplug the MAF (by the airbox) and check and clean the pins on both the MAF and the harness connector.

Good luck.