What is the specified engine speed for the throttle opener servo diaphragm check?

The servo-diaphragm is functioning properly if engine speed comes into the specified range of 1,650 - 1,850 rpm.

How do I adjust the servo diaphragm if engine speed is out of range?

Use the servo-diaphragm adjusting screw: turn it clockwise if engine speed is lower than the prescribed range, and counterclockwise if it is higher.

What do the vacuum hose colors mean on this emission control system?

Yellow is the vacuum line to the distributor, White is the vacuum line for the E.G.R. system, Green is the manifold vacuum line, and Pink is atmospheric pressure.

How far should a vacuum hose be inserted onto a pipe?

When inserting tolerance is not limited, insert 15 - 20 mm (0.59 - 0.79 in). If a stopper is equipped, insert the pipe until it stops. If the pipe has a bulge, insert the hose up to the bulge.

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Nissan Throttle Opener Control System (TOCS) Adjustment & Vacuum Hose Color Code

T.O.C.S. servo diaphragm stroke check and emission vacuum hose color code, Nissan EF & EC

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TOCS servo-diaphragm stroke set to 1,650-1,850 rpm, plus emission vacuum-hose color code: yellow=distributor, white=EGR, green=manifold vacuum, pink=atmospheric.

AI caption June 2005 · Photo 132 of 412

This is a scanned page (EF & EC-32) from a Nissan factory service manual section on Exhaust Emission Control, specifically the Throttle Opener Control System (T.O.C.S.). The left column continues an Inspection and Adjustment procedure for the servo diaphragm stroke: connect a tachometer, warm the engine to operating temperature, disconnect the rubber hose between the servo-diaphragm and vacuum control valve, then connect the hose to the intake manifold. The servo-diaphragm is functioning properly if engine speed falls within the specified range of 1,650–1,850 rpm; if not, the servo-diaphragm adjusting screw is turned clockwise to raise speed or counterclockwise to lower it. Two line drawings (SEC724 and SEC260A) identify the throttle opener servo diaphragm, adjusting screw, lock nut, and link on the carburetor. The right column covers Vacuum Hoses, explaining the color coding of emission control hoses (Yellow = vacuum line to distributor, White = EGR system vacuum line, Green = manifold vacuum line, Pink = atmospheric pressure) and hose insertion practices: insert 15–20 mm (0.59–0.79 in) when tolerance is not limited, insert until it stops when a stopper is equipped, and insert up to the bulge when the pipe has a bulge.

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Frequently asked questions

What is the specified engine speed for the throttle opener servo diaphragm check?: The servo-diaphragm is functioning properly if engine speed comes into the specified range of 1,650 - 1,850 rpm.
How do I adjust the servo diaphragm if engine speed is out of range?: Use the servo-diaphragm adjusting screw: turn it clockwise if engine speed is lower than the prescribed range, and counterclockwise if it is higher.
What do the vacuum hose colors mean on this emission control system?: Yellow is the vacuum line to the distributor, White is the vacuum line for the E.G.R. system, Green is the manifold vacuum line, and Pink is atmospheric pressure.
How far should a vacuum hose be inserted onto a pipe?: When inserting tolerance is not limited, insert 15 - 20 mm (0.59 - 0.79 in). If a stopper is equipped, insert the pipe until it stops. If the pipe has a bulge, insert the hose up to the bulge.
What are the first steps of the servo diaphragm stroke inspection?: Connect an engine tachometer, warm up the engine to operating temperature, disconnect the rubber hose between the servo-diaphragm and vacuum control valve, then connect the rubber hose to the intake manifold.