So I recently bought an 86 z31 and it's my first car with a turbo. I noticed that the boost wasn't going past 0 and tried checking as many of the vacuum lines as I could find. I can hear the turbo spooling, so I don't think that is the issue quite yet. I also hooked up a different gauge temporarily to check if it was my gauges, but still got the same readings.

I think the the issue is the boost gauge above the radio, since it only works sometimes. I'm not sure if this is a vacuum line, or if it runs off the boost sensor under the hood like the dash. Either way, both of those read just below zero just like the aftermarket one did.

I tightened some loose connections going to the brake booster, and it seemed to help a bit, but the boost still didn't get over 0.

I'm going to try and cap off and pressurize to see if it is indeed a leak, or maybe narrow it down to the wastegate. Would the intake be the best place to do this? Is there an easy way to check the wastegate?

Thanks for the help, loving the z31 otherwise.

 

where are you putting the gage? analog or digital dash? take the safety valve screwed into the front right edge of the plenum and put a one inch pipe plug in its stead. that will assure that at least you aren't losing boost there. vacuum lines and brake booster got nothing to do with boost except peripherally. Reach up under the car and manually move the waste gate. unless stuck open it is probably all right. simple mechanism. in what running mode are you looking at the boost. You need to find a long incline and floor it in second or third (going up hill) to actually see any boost. just cruising down the hwy mine runs about 18 inches of mercury. only time I see much boost is waving goodbye to a honda with a six inch tailpipe. check the rubber piping going to and coming from the turbo. people have found cracks there. is your air filter clean? have you checked the fuel pressure? timing?
here is some stuff that will save headaches down the line
Get your battery load tested. Be sure you have clean, tight corrosion free terminals on both ends of your battery cables. Be sure the ground (negative) cable goes to a bolt into the frame before going to the starter. grounding through the starter is not a reliable connection. Z's don't like low voltage. causes the electronics to act funny. it is possible to have enough amps to crank but not enough voltage to run the electronics. If you have one size fit all cheapo clamp on terminals they are a problem waiting to happen. Usually on a rainy night around Oh Dark Thirty.

Clean the connectors for the maf or afm, ecu and tps. Deoxit by CAIG is probably the best connector cleaner on the market. spray with CorrosionX after cleaning and before putting together this will help prevent any further corrosion. DON'T USE DIELECTRIC GREASE.

Replace outer tie rod ends, and ball joints. replace the bushings with poly (don't forget to lube them as directed unless you like squeaky things). New shocks. Get new boots for power steering. all those things will make you think you are driving a different car. doing them piece meal is a waste you won't see a great improvement until you do the complete job. You need to get the car realigned after messing with the front. Have your tires in good shape and rebalance. Rear bushings nice too but more work and you won't notice as great an improvement. Rear shocks also because if the fronts are gone so are the rears. if car squats when you jump on the gas the rears are gone. If you have the electro adjustable shocks they are DEFINITELY GONE.

 

Oh yeah the 86 is the best looking of the z31's in my opinion so congrats on that. get the fsm from xenon and read it. stock vac gage probably useless unless you got the digit dash in which case you don't have a stock vac gage. nice to put little details like that in your post makes it easier to pass on some help