Although the PCV valve is a simple device, it is designed to reducethe air pressure inside the engine and redirect it to the air intake system.Since the air is contaminated with oil and gasoline, this does in timeaffect the operation of the valve assembly. The valve will plug up overtime, which can result in a poor running engine that delivers less power,or fuel economy.

The PCV valve may fail in either a closed or open position, usuallydue to clogging with oil sludge or dirt. Failing in the open position causeshard starting and rough, low speed running. Failure in the closed positioncauses buildup of crankcase pressure, which can force engine oil past seals,gaskets and other openings in the crankcase. Most likely through the rearmain seal, or blowing out the dipstick on the Z32.

This isn't listed as an interval replacement item, but I'd replace themevery 60k miles. This is the procedure done on JeffB's '91 TT at 68k miles.He says it made a noticeable difference in the performance of his car.

Special Tools:
Couple different pairs of long bent needle nose pliers (straight, 45 degree, 90 degree)
Hacksaw blade
Magnet on a sitck, or the flexible fingers on a stalk to retrieve dropped sockets

Part Numbers:

11810-40P00 PCV valves (2 req'd)
11823-30P01 & 11823-30P11 side PCV hoses
Entire PCV replacement kit (all 5 PCV hoses, etc.)

Procedure:

1. Remove the battery: Disconnect the negative battery terminal (1 x 10mm). Remove the cowlpanel above the battery (4 x phillips plastic clips). Remove the positivebattery terminal (1 x 10mm). Remove the battery holding strap (2 x 10mm).Remove the battery and set on a wooden block to keep from discharging.

2. Remove the passenger PCV hose: Locate the PCV valve on thebottom side of the intake plenum pointing towards the rear on thepassenger side. Remove the rear clamp on the PCV hose (red dot in 1.),slide it back off the hose onto the metal tube. Carefully use ascrewdriver between the tube and the plenum on the back side to pry itout of the hose. Twist the hose around to get to the clamp on the frontof the hose. I was able to just pull it off (2.). Use long needle nose pliers to reach in there and squeeze the clamp to pull it off if necessary. Remove the hose.

3. Remove the passenger PCV valve: Note the amount of threadsexposed on the valve from the plenum before removing it. Use a deepsocket and short extension to remove the PCV valve out of the plenum(red dot in 3.) (1 x 19mm). Be careful not to drop it further into the engine bay.

4. Install the new passenger PCV valve: Use a smaller socket(10mm) inside the 19mm deep socket to keep the new PCV valve stickingout far enough from the socket to engage the threads in the plenum (4.).Tighten the PCV valve until it's snug, there will be about 2-3 threadsleft exposed. Put a slight bit of oil on the inside of the new hoseends to aid in slipping it back in place. Put the large hose clamp onthe front of the new hose & twist it around to where it isaccessible when re-installed. Slip the hose onto the valve. Put thesmaller hose clamp on the rear of the hose & pry the rear tubeback, then slip it into the end of the hose. Get both hose clampssettled in place (5.).

5. Check all the hoses in the area: The '90-'92 have the AIVsolenoids in the area, lots of small hoses can possibly  be knockedloose or broken. Reinstall the battery & cowling. Reconnect theterminals.

6. Make access to the driver side PCV valve: The driver side isa little more difficult. Doing the passenger side first shows what thebasic operation is about. Remove the idle air tube (red dot in 6.). To get it out of the way, remove the bolts on the balance tube (2 x 12mm) (7.)and the cable guide at the front (1 x 10mm). The engine wiring harnessruns underneath it and should be supported by 3 clips. Use a flat bladescrewdriver to pop the tabs and slide them off the bottom of the tube.Disconnect the brake booster vacuum line (red dot in 8.), flipit up out of the way. Disconnect the two small vacuum hoses. Slide thehose clamps on the front hose forward and squeeze the clamp on the idleair control valve on the back of the plenum. Remove the idle air tubewith the short 90 degree bent hose on the rear end. Disconnect theremaining hoses from the two hex hose fittings on the side of theplenum. Remove the lower fitting using a crescent wrench (9. is the top one, 10.is the bottom one being removed). I use a zip tie around the upperfitting and the wiring harness to pull it up and out of the way. Thereshould be resonable access to the PCV valve and hose.

7. Remove the driver PCV hose: Use a hacksaw blade to cut thePCV valve hose in half. Slip the hose clamps off using the mostappropriate set of needle nose pliers. Sometimes the clamps get put onin odd directions, because it makes most sense when the engine is outof the car, but makes it difficult when the engine is back in the carto access them. Cutting the hose should allow the clamps to be twistedinto place. Remove the split hose leaving the front and rear fittings(red dots in 11.).

8. Replace the driver PCV valve: A deep 19mm socket on a swivelwith a 9' extension is the easiest way to get the PCV valve out (12.).Use the same socket in a socket trick to get the new valve installed.This is very tricky, be patient, there's little room to move your handsand tools in there. Be careful not to drop the socket in the enginebay.

9. Install the new driver PCV hose: Lightly oil the insides ofthe new hose. The rear fitting can swivel a little bit up and down(it's a swedge fitting to the valve cover). Use this as an advantagewhen installing the hose. Put both hose clamps on the hose, orientedwhere they can be squeezed on for installation. Slip the hose in place& get the clamps settled (13.).

10. Reconnect hoses, etc.: Reinstall the hex fitting andassociated hoses. Reinstall the idle air tube and hoses (2 x 12mm, 1 x10mm, 2 x hose clamp). Re-attach the 2 small vacuum hoses and the brakebooster hose (1 hose clamp).

REV: 10-15-2003