[Biturbos4] HELP!!! Troubleshooting DTCs w/ EPC light

David Kavanagh dak at rochester.rr.com
Sun Nov 28 18:39:27 EST 2004

Good question. I know on some cars, the crank case is under vacuum, but 
don't think that is the case here. Still, if they suck crank case gasses 
into the intake, that would mean that extra air entering via the valve 
cover gasket might cause problems... Still, my MAF is really out of whack...


Thus Spoke John:

> David Kavanagh wrote:
> > Thanks. I did check for boost leaks (see this :
> > http://home.rochester.rr.com/dak/leakcheck/)
> > I ended up replacing the leaking valve cover gasket. I haven't tried to
> > re-pressurize the system since. I also wonder if it is really valid to
> > pressurize at the point I did. I mean, the part between teh MAF and the
> > turbo intake is generally under vacuum. Still, 10 psi can't be a bad
> > thing to test with. If it leaks at that pressure, chances are I'd 
> have a
> > vacuum leak when running!
> I was baffled by your fix until I noticed that your said: "...the part 
> between the MAF and the turbo intake...". While the valve cover leak 
> was probably a good catch, I'd assume that won't affect your problem. 
> Don't most cars, including Audi, have any number of check valves and 
> air hoses between the crankcase, fuel vapor system and the intake to 
> burn vapors for emission control?
> John

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