TOYOTA PREVIA 91-97 REPAIR MANUAL

4-6 DRIVEABILITY AND EMISSIONS CONTROLS

Intake Manifold Sic e

Clean Hose

Fig. 5 Blow air from the air manifold side, check that the

passes with difficulty

1. Remove the PCV valve from the valve cover or intake manifc]d, but
   leave it connected to its hose.


2. Start the engine.


3. Place your thumb over the end of the valve to check for vacil urn. If
   there is no vacuum, check for plugged hoses or ports. If these areibpen, the
   valve is faulty.


4. With the engine OFF, remove the valve completely. Shake iljend-to-
   end, listening for the rattle of the needle inside the valve. If no ratt e is
   heard, the needle is jammed (probably due to oil sludge) and the '|alve
   should be replaced.

CAUTION

Don't blow directly into the valve; petroleum deposits w thin the
valve can be harmful.

An engine without crankcase ventilation is quickly damaged. It
tant to check the PCV at regular intervals. When replacing a PCV
must use the correct one for the engine. Many valves look alike o
side, but have different mechanical values. Putting the incorrect v
vehicle can cause a great deal of driveability problems.

REMOVAL & INSTALLATION

1. Remove the RH seat and No. 2 cylinder head cover.
   a. Remove the 3 screws and scuff plate.
   b. Remove the bolt and disconnect the RH seat belt from th front
   floor panel.
   c. Remove the 4 bolts and the RH front seat.
   d. Extract the 2 bolts and the RH front seat leg.
   e. Remove the 2 bolts and the jack holder.
   f. Unbolt the RH engine service cover.


2. Locate and remove the PCV valve.


3. Inspect the PCV valve operation.


4. Check the valve for proper operation. While the valve is jfemoved,
   the hoses should be checked for splits, kinks and blockages. Cj leek the
   vacuum port (that the hoses connect to) for any clogging.


5. Inspect the rubber grommet the PCV valve fits into. If it is fi any way
   deteriorated or oil soaked, replace it.
   To install:


6. Reinstall the PCV valve.

s impor-

alve you

the out-

veon a

Fig. 6 Leaks from any of these areas can cause the PCV system

to malfunction

7. Attach the RH engine hole cover.


8. Install and secure the No. 2 cylinder head cover and RH seat,
   a. Tighten the bolts to the following specifications:

• Service hole cover bolts—10 ft. Ibs. (14 Nm)


• Jack holder—10ft. Ibs. (14Nm)


• RH seat leg—29 ft. Ibs. (39 Nm)


• RH seat—29 ft, Ibs. (39 Nm)


• RH seat belt-to-floor pan—31 ft. Ibs. (42 Nm)

Evaporative Emission Controls

OPERATION

The Evaporative Emission Control (EVAP) system is designed to prevent

fuel tank vapors from being emitted into the atmosphere. When the engine

is not running, gasoline vapors from the tank are stored in a charcoal can-

ister. The charcoal canister absorbs the gasoline vapors and stores them

until certain engine conditions are met and the vapors can be purged and

burned by the engine. In some vehicles, any liquid fuel entering the canister

goes into a reservoir in the bottom of the canister to protect the integrity of

the carbon element in the canister above. These systems employ the follow-

ing components:

• Fuel tank cap


• Charcoal canister


• Check valve


• Vacuum Switching Valve (VSV)—2TZ-FZE only

COMPONENT TESTING

» See Figure 7

Before embarking on component removal or extensive diagnosis, per-

form a complete visual check of the system. Every vacuum line and vapor

line (including the lines running to the tank) should be inspected for crack-

ing, loose clamps, kinks and obstructions. Additionally, check the tank for

any signs of deformation or crushing. Each vacuum port on the engine or

manifold should be checked for restriction by dirt or sludge.

The evaporative control system is generally not prone to component fail-

ure in normal circumstances; most problems can be tracked to the causes

listed above.