Completed my first plenum pull yesterday! Everything went back together nice and smooth, fired her up, and she had a HUGE air leak somewhere at the back center of the engine that was eventually killing her at idle. My pipe that runs from the IACV to the Balance tube had a small crack in the end of it, so I initially thought it was that not getting a good seal, and for leaning over the running engine and listening, it sounded right, but I didn't feel any leak with my hand. Plus she was struggling at idle, which made sense with a bad IACV connection. Anyways, I put in an order for a replacement hose, and was happy to sit on it a couple of days until the hose arrived.

Last night, literally in the middle of the night, I woke up with an 'oh s***' moment. I did the EGR Bypass Without Removal http://z32.wikispaces.com/EGR+Removal#P ... %20Removal where you cut back the EGR pipes to the plenum, and pull the solenoid and vac lines, but leave the valve in place. As I was happily removing everything, I pulled the EGR solenoid to hard pipe behind the plenum line, then the hardpipe to EGR Valve line. I didn't cap the vacuum connection to the EGR valve.

So, I'm wondering, am I allowing exhaust or something else to leak out of the EGR valve by not capping that vacuum connection? Am I going to have to dig my hand back there and try to find that stupid vac line connection to cap it off?

Not that I think it matters here, but list of work done: Plenum Coolant Line Bypass, EGR Bypass w/o Removal, AIV delete, Valve Cover gaskets redone, new injectors

Ok so let me see if I understand this correctly from your description... you did the EGR bypass without removal deal, where you cut the 2 tubes going from the plenum to the EGR valve. I'm assuming you put the block-off plates on the underside of the plenum and then capped the cutoff egr tubes?

As for the vacuum lines, you should have completely bypassed the egr solenoid and egr valve. Usually you just remove the 3 vacuum lines completely and then run 1 line from the throttle body nipple to the metal T connection on the side of the plenum.

I tried editing that NA vacuum diagram to show it better:



The X's are the stuff you remove and the black line I drew in is where you should put in a vacuum line. You're supposed to cap off the egr valve nipple, but if you just remove other end of the vacuum line from the egr solenoid and cap that it should be fine.

This is the current state of my vacuum lines. Actually I realized after posting that I've removed the 2 hardlines on the passenger side of the plenum, but they're still showing atm:



EGR/AIV Solenoids gone, all lines rerouted appropriately. The EGR Valve had a line going to it, which I removed, but I didn't cap or block off at the valve. The underside of the plenum does have the block plates. The pipes running from the Valve to the underside of the plenum are cut and capped.

My bad I didn't even realize you had a TT and I'm sitting there showing you the NA diagram. Anyway, the vacuum line for the egr valve is just to tell it when to open/close. If there is no vacuum line attached to it then it can't receive vacuum so the valve can't open. Capping it is recommended, but since your egr tubes themselves are capped it wouldn't matter if the egr valve received a vacuum signal or not because the exhaust gases wouldn't be able to go anywhere. Since the egr valve is basically only attached to the exhaust now, it shouldn't be able to cause a vacuum leak or even an exhaust leak (since the tubes are capped).

Alrighty, thanks sir! I'm hoping you're right and that my initial diagnosis of bad IACV hose was correct. We'll see in a couple days.

FYI, I've seen a couple of EGR valves go bad over the years. One cracked diaphram and the other, not sitting in the closed position, due to crap stuck in there.

itsa300zx wrote:FYI, I've seen a couple of EGR valves go bad over the years. One cracked diaphram and the other, not sitting in the closed position, due to crap stuck in there.

If I had no reason to believe the EGR system was malfunctioning before the delete, and I didn't wrench/cut on the valve itself, is there much reason to believe something may have changed?

Even if the valve itself failed, it can't do anything because the tubes are capped. Therefore it can't leak any exhaust gases into the plenum or anywhere else.

Are you sure you didn't nick any other hoses or vacuum lines when you were cutting the tubes? The pcv hoses sit pretty close the egr tubes I think. I guess it depends what you cut the tubes with. I would just install the new IACV hose when it gets there and then double check that all the other hoses and vac lines are good and tight. If it persists after that you might be buying a boost leak tester.

t.mcginley.jr wrote:Even if the valve itself failed, it can't do anything because the tubes are capped. Therefore it can't leak any exhaust gases into the plenum or anywhere else.

Mostly true, except if the valve is stuck open, then the exhaust gas would leak to the pipes he cut.

The sound is coming from the back center of the engine/plenum area right now, not around the sides where the pipes are cut and capped. Although it is capped, if something wanted to really push, I'm sure it could leak out, they're just 5/8" rubber caps zip tied to the pipes. I'm just going to wait with my fingers crossed that this new IACV hose fixes things up. That would make me happy!

ThisIsSparTTa wrote:The sound is coming from the back center of the engine/plenum area right now, not around the sides where the pipes are cut and capped. Although it is capped, if something wanted to really push, I'm sure it could leak out, they're just 5/8" rubber caps zip tied to the pipes. I'm just going to wait with my fingers crossed that this new IACV hose fixes things up. That would make me happy!

AHH I see, Ignore my comments:)

How did this turn out? I'm curious

The EGR valve wasn't the source of the problem although I did eventually cap it when the plenum was back off. It turned out to be the lower injector ring on #6 had rolled up, simultaneously blocking fuel coming in and not sealing up properly. I fixed this and a couple of other things, got to drive her for about 25 minutes then got a bent rod or spun a bearing. I will be rebuilding soon

Just thought I would throw out there that you can just use 1/2 inch heater hose for the IACV line, just did it the other day so I know it works and you can get it anywhere for dirt cheap.