cb951

I ground down the pad on the IM where it sits on the rear support near the oil filler. No longer have a high point issue. Put it all back together and a pressure test still shows a leak at the #4 intake runner-to-head.

Slept on it for a couple days...Did some more RL research (I think I've read all of the threads in my searches several times.)

Then I re-read a couple posts which highly recommended disconnecting and plugging the hose from the j-boot to the AOS, so that the crankcase isn't pressurized. What do you know...The leak from the intake is gone!

So...I think that leak must be from the cam housing right next to the #4 intake runner. But it doesn't leak oil.

Well, with the breather hose disconnected from the j-boot and the boot plugged, I can build pressure. 5 psi, no problem...When I get to 10 psi, the plastic purge valve near the fuse box starts to hum. I know it's not designed to see pressure, and I think the 10 psi caused the valve to open a bit, causing a pressure loss. If I disconnect and plug the small hose from the j-boot to the metal purge control valve (thereby bypassing the purge system), I can build 10 psi without an immediate loss. (Takes about 15 - 20 seconds from 10 psi to 5 psi, then about another 20 seconds to go to 0 psi.)

At that point, I found a leak at the seam on the body of the fairly new Evo Motorsport bypass (BOV) valve (from Paragon). Would that cause any problems? Does it ever see pressure? Should I replace it? (I have the original valve installed for now. I doesn't leak externally, but does leak a bit through the diaphragm.)

I couldn't hear (with a hose to my ear) any other leaks from anywhere in the engine compartment. After starting the engine and idling until warm, my warm idle vacuum is now down to 15 inHG (from 19 inHG before I started any of this, and from 17 inHG after my first pressure test.)

I'm going to take it for a test drive tomorrow to see if there are any other issues. I still need to set the idle (with the ISV bypassed). Should I wait until vacuum issues are ALL gone?

Are the underdash vacuum bits accessible, or do I need to pull parts of the dash apart? I guess I can disconnect the line from the check valve in the large brake booster vacuum line and check that section with a MightyVac hand pump. Right?

I'm really trying to not get too discouraged, but it's getting difficult. Seems that every time I or several Porsche shops have worked on the car, it just seems to get worse. Of course, I've been trying to get the car really "correct" lately, but it's always run very well (and it only has 61k miles on it). I just want it to be safe and reliable for the track as well as for the street.

JustinL

I'm glad you are getting things sorted out. 15inHG isn't "bad", and could mean a few different things depending on atmospheric pressure in your area. I am currently running a similar vacuum setup to you with almost everything under my manifold removed. The only vacuum lines left that I have are the bare essentials. My atmospheric pressure here is about 93kpa and I pull about 32kpa at idle. That translates to either 19inHG or 21inHG depending on how you calculate it.

If you delete your ISV, grab some caps and cap the port on the manifold and on the hard pipe. You will need to use the gas pedal to keep it running when it's cold. If you have a cycling valve, check that for leaks too. The other thing to remember is that the screw on the throttle body is how you are going to set your idle and will directly affect your vacuum reading. If you want to test things out, plug each of your vacuum lines one at a time with your finger and watch the manifold pressure at idle.

Try pulling a vac directly on your bypass valve and see if it can hold. If you can pull air through the vacuum line then that will contribute to leakiness.

Justin

cb951

Thanks for following my thread, Justin. I appreciate the advice and encouragement.

My main concern is that the vacuum at warm idle is lower than it was when I started all of the venturi delete and vac hose replacement. EVERYTHING under the IM is new, including ISV (and I tested it for leaks by blowing into it with the other port blocked before I installed it). Cycling valve had already been deleted, running a Greddy Profec B Spec II EBC and a TiAl 38mm WG).

I know that the bypass valve (Evo billet) leaks at the seam on the body of the valve. I switched in the original valve which leaks internally through the diaphragm and my warm idle vac is still at 15 inHG. I'll definitely replace it with a new Evo (lifetime warranty -- I've emailed Paragon). But the leaky Evo valve was in when I had 19 inHG.

Since I resealed the throttle body with the Arnworx kit from Paragon, I'm sure I need to reset the idle with the ISV bypassed. When I reassembled the TB, I installed the idle adjustment screw the same number of turns as it took to remove, so right now I see no difference in idle speed, but I know that the ISV will compensate to get the idle consistent. Should I adjust the idle speed now or should I wait to get all of the vacuum issues squared away? Is it possible that the idle speed adjustment would change my warm idle vacuum? If so, that might be my current issue.

Beyond all of the previous, is it possible to lose vacuum (or pressure during a test) through the intake/exhaust valves and out the exhaust? I've never blocked off the exhaust during any testing.


I took the car for a test drive today (just around town), and it seems to run fine, just like it did before. AFRs, however, seem a little richer while cruising before settling in around 14.7. Seems slower to get back to 14.7. Seems consistent with vac leaks. No idle or acceleration issues. Same popping out the tailpipe on decceleration/shifting (which started after the 951MAX chips, exhaust, WG, etc. were installed).


I think I need to take another short break from the car. It's making my head hurt.

JustinL

Absolutely. All that screw does is give you a controlled (and metered) vacuum leak. On my car, if I crank it down too far it stalls the car. If it's too high the idle goes up, but there is a range where the idle changes very little, but you can get more vacuum. That's how I set it. Get the car warmed up and turn the screw until the idle dips and the engine stumbles. Back it off a bit and you're done. With that setting though, the car will want to stall when it's cold, so you have to keep your heel-toeing sharp until it warms up.

Popping out the exhaust is weird on decel. There should be fuel cut when you get off the gas. Either your chips are mapped to give fuel (probably very lean) on decel or your idle switch isn't working. I've found that 14-15.5AFR gives a burbly exhaust, 16-18 gives loud pops. Rich gives woofs.

cb951

EDIT: I thought my EBC was set to read vac in kPa (and the conversion to inHG would have been 21 inHG), but it's in psi. So the conversion to inHG is consistent with my AutoMeter vac/boost gauge. I am getting 14 - 15 inHG at warm idle.

Next step is to check CO at warm idle (with O2 sensor disconnected). Then to set the idle with the ISV bypassed. Will recheck my vac again after that.