Quote:
Originally Posted by ike84
Before you bust out that smoke machine I would look at some vacuum diagrams so you're familiar with the system. The vacuum houses, changeover valves, vacuum resivoir, etc are kinda complicated - not so much in theory, just in the layout. Hairline cracks in the vacuum resivoir, for example, have driven people to the brink of insanity. If you go over everything with the smoke machine and get nowhere I would bust out the brake cleaner to double check. Good luck!
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Hey! I've had the plenum, throttlebody and resonator tube off quite a bit and I'm actually pretty familiar with the routing of the vacuum lines. It appeared to be messy to me the first time or two I looked at it, but it's actually pretty straightforward! That said, I take your point, especially with respect to the smoke machine.
I'm fairly certain it's not the reservoir, because if I pull the vacuum line between it and the one-way valve after running the car, I can hear it suck in air. Perhaps I'll get in there and just test lines and y-fittings with my hand pump because it's easy to do and doesn't stink like the smoke machine. I also wouldn't mind some information on how to test the change-over valves. I have a 12V power supply and the ability to regulate voltage, so I'd like to actually test them for operation. I'll keep looking.
All this said, I just pulled 10 psi of vacuum at the fuel pressure regulator which is pretty healthy intake vacuum, if I am not mistaken. Porsche troubleshooting manual for checking fuel pressure regulator operation specified 6-9 psi of vacuum on this hose. I HOPE it's a vacuum leak, but at this point, with RKAT at -3.5, it appears this motor is running rich at idle, not lean like I'd expect for a vacuum leak.
To further muddy the waters though, when I used my cheap bluetooth OBD-II with Torque Pro, the LTFT (not divided into RKAT and FRA in Torque app) showed that they were pegged POSITIVE for both banks, which would support a vacuum leak.