I think I have a Boost leak. One thing I've noticed is that no matter what I do I can't seem to get my boost to say steady. I probably need to mess around with the setting on my Profec B-spec II more, but right now I peak at 10.9 psi and then bleed off to about 8.8-9psi. So I was wondering if maybe it was my settings or what, so I set the controller to the low setting which would be stock and then just while cruising oh the highway floored it. My Boost peaked according to the controller at 6.9. Sounds about right for stock. 6.8-6.9psi, and then bled off to about 6.1-6.2 psi. I'm wondering if I have a boost leak or what. I can't seem to find vacuum leaks, and I've done many times before spraying brakleen around areas and not noticing a change in idle sound. This might possibly be the source of my random misfire at idle not to mention why my car feels a bit slow and didn't seem to be a big improvement when upping the boost to 10. Plus I always notice after hammering the throttle I'll get a potent smell of fuel which would probably indicate I'm running really rich.

Oh, I was also thinking could an ignition problem also be the cause of boost bleeding off? I know it could certainly be the cause for it smelling alot more rich. At idle my vacuum fluctuates a little. My map readout will fluctuate a little between 18.7-19.0 inHG of vacuum. I attribute the just slightly lower vacuum to the fact that I had to adjust the throttle stop open a bit more to keep the car idling after removing the AAC and what not. Maybe I'm incorrect.

 

Hum... sounds like either a weak waste gate or an issue w/ the boost controller and or hoses. Have you tried removing the boost controller & running stock boost on stock vacuum lines?

I assume you have removed the emergency release valve on the intake mani?

 

Yeah, I have removed and plugged the pop-off valve. That's a thought though, maybe I'll try putting stock lines on. I did remember too that the one time when I got on the freeway and hammered it on the ramp my friend's behind me said there was a bunch of black smoke that came out the exhaust indicating running rich.

 

Have you removed any emissions equipment? I noticed my Z ran richer when I did it as an experiment. It would idle in the 12-13 afr range, and boosting would always be in the low 10s or lower. I put my stuff back on, and the issue went away.

You can check for boost leaks by pressurizing the system using a bike pump and sealing one end off. Listen for hisses, if there are none, you're fine. What is your fuel pressure at? Timing? I know you're using Nistune, but did you add or subtract fuel in the maps, or are you running the stock tune still?

 

Currently I'm running the stock 1987 300ZX tune. I figured I'd run it for the winter as it'd probably be better suited. I've removed the AAC and VCV from my intake manifold. When I removed those my car would barely idle so I had to adjust the throttle stop to get the car at the proper idle. When the motor comes out in the spring or summer for my swap I'm going to redo my intake/exhaust gasket and get my exhaust manifold resurfaced as well as switching to my N42 intake. Last time I checked my fuel pressure was at factory spec. I haven't checked in a while. I need to hook my fuel pressure gauge back up.

 

^^^ Put your AAC back on. My car will not idle (warm) with that removed & covered. This is the huge dilemma w/ removing the AAC / using the N42. The 280zx turbo does not like to idle w/o it. Bleach pulled it off somehow by blocking everything & routing the j-pipe extra tube direct to the back of the air regulator. I haven't tried that yet....

 

Hmm, if you're running the stock tune, let me know what your afr's are on a 3rd or 4th gear pull on your wideband for both stock and at your ~11 psi run. I wrote down in a notebook the values I had on the stock tune for up to 12 psi when I first went with the Z31 setup. I'm at work right now so I won't have access to it right away.

Also, are you running with the stock exhaust? Just a thought, but if your exhaust is a restriction, it could cause you to lose some psi up top as you'll be outflowing your muffler. Just a note, that my Z peaks at 1.35 bar of boost, but settles to ~1.25-1.3 bar by 6000K rpm. I believe my turbo is too small on the hot side.

 

Yeah I have the stock exhaust and the catalytic converter. As for the AAC I did just like Bleach did. I plugged off the VCV and the AAC and just routed the hose from the J-pipe directly to the air regulator. At first I had idling issues. It would just idle way to low and either die or just idle really poorly. Then that's why I adjusted the throttle stop little by little until I had about normal idle.

 

One more thing comes to mind is to inspect your catalytic converter. If it gets clogged it will make you lose boost and/or power, especially as the revs get higher. Take it off and shine a droplight through it. If you can see the light without much of a problem, you're fine, but if it's obscured, your catalytic could be breaking down and on its way to failure.

 

Hmm, that's a thought. It would only have just under 98k miles on it, but it would be 26 years old.

 

Yeah, mileage usually doesn't matter, it's what happens during those miles. Short trips will definitely kill it as well as WOT runs. Another thing when inspecting it is you should not see light on the outer edges of the honeycomb matrix, only down the middle. If you do see light on the outer edges, replace your cat asap. Otherwise you'll soon be dumping chunks of ceramic out of your pipes and muffler.

 

a good portion of my drives have been short trips. I live a mile and a half from work. So yeah... I'll have to check it out sometime soon.