Pages 4-83, 4-84
1986
Carburetors, Fuel Charging Assemblies and Throttle Bodies 4-83
Idle Mixture Setting Procedures
IDLE FUEL MIXTURE-PROPANE ENRICHMENT METHOD
Passenger Car. 1.9L w/740-2V, 2.3L OHC w/YFA-IV FB, 2.3L HSC w/1949-IV, 3.8L w/2150-A-2V and 5.0L w/4180C-4V.
Truck, Under 8500 GVW: 5.8L w/4180C-4V.
NOTE: This procedure is applicable to the above engines only. If CO and HC are not within specification, perform appropriate electrical diagnostic procedure in Section 15.
I. Vehicle Preparation: All Carburetors as noted above.
A. Apply the parking brake, and block the wheels. Disconnect the automatic brake release, if so equipped, and plug the vacuum connection.
B. Connect an analog tachometer, Rotunda 059-000010 or an equivalent analog tachometer.
C. If so equipped, insure that the hot idle compensator is in a closed position and remains so throughout the test. Idle vehicle on kickdown step of fast idle cam for three to five minutes to insure that HIC valve is closed.
D. If so equipped, disconnect the fuel evaporative purge hose at the engine or the carburetor, (1.9L engines) and plug the connection. (Not applicable to 5.0L and 5.8L Truck and 5.0L Passenger Car engines).
E. If so equipped, disconnect the fuel evaporative purge hose at the air cleaner and plug the nipple. (Not applicable to 5.0L and 5.8L Truck and 5.0L Passenger car engines).
F. Disconnect the flexible fresh air tube from the air cleaner duct or adaptor. Using propane enrichment Tool T75L-9600-A or equivalent, insert the tool hose approximately 3/4 of the way into the duct or fresh air tube. If necessary, secure the hose with tape.
G. For vehicles equipped with thermactor systems, revise the dump valve vacuum hoses as follows: (Not applicable to 1.9L engines).
1. For dump valves with two vacuum fittings, disconnect and plug the hose(s).
2. For dump valves with one fitting or combination air bypass/air control valve, remove the hose at the dump valve and plug it. Connect a slave hose from the dump valve vacuum fitting to an intake manifold vacuum fitting. (Not applicable to 5.0L and 5.8L Truck engines with 2150A-2VFB).
3. For 2.3L OHC engines:
a. Equipped with a dump valve with two vacuum fittings: Disconnect and plug the hoses.
b. Equipped with a combination dump valve and air diverter valve: Disconnect and plug the hoses (2-port) from the dump valve portion.
c. Equipped with feedback carburetor: Disconnect electric lead wire from electric PVS.
4. On 3.8L engine Canadian 2150A-2V applications, do not make any thermactor system modifications.
5. For 5.8L 4180C-4V Truck Disconnect and Plug Vacuum Hose to Dump Valve.
1986
4-84 Carburetors, Fuel Charging Assemblies and Throttle Bodies
Idle Mixture Setting Procedures
H. For 1.9L ATX/MTX vehicles equipped with (Mechanical Vacuum) Idle Speed Control (ISC):
1. With engine off:
a. Disconnect and plug the vacuum hose at the MVISC.
b. Connect an alternate vacuum source (hand vacuum pump) capable of maintaining 22 inches Hg. to the ISC diaphragm on carburetor, and apply vacuum (retracting ISC plunger clear of throttle linkage).
2. With engine running and transmission in Drive (ATX) or Neutral (MTX):
^ Idle speed should be equal to the ISC retracted speed specified on the emission decal, if not readjust throttle stop adjustment screw under choke housing to specification, (fan On, A/C Off).
I. When the above Steps have been completed, proceed to Section II.
II. Propane Enrichment Method (Except as Noted)
NOTE: Leave all vacuum signal hoses attached to the air cleaner assembly when relocating the assembly to perform carburetor adjustments. The air cleaner assembly must be in place however, when measuring engine speeds.
CAUTION: Prolonged engine idling can result in catalyst overheating and excessive underbody temperatures.
A. Verify that the timing is set to specification; reset if necessary, Section 15.
B. Check engine curb idle rpm or A/C-off rpm, and, if necessary, reset to specification, Section 4.
NOTE: Even If the vehicle has less than 160.9 km (100 miles) of operation, set the speed to the normal engine specification.
NOTE: Remove PCV valve from grommet, and allow PCV valve to draw underhood air during idle fuel mixture check. (PCV should remain in vertical position).
NOTE: Escort/Lynx, has an in-line fixed orifice crankcase vent, not a conventional PCV valve. The fixed orifice is located in the crankcase vent hose located between the vacuum fitting on the intake manifold and the plastic fitting attached to the air cleaner tray.
Locate the crankcase vent hose and disconnect at the air cleaner end, allowing the hose to vent to underhood air during idle fuel/air mixture check.
C. With the transmission in Neutral, run the engine at approximately 2500 rpm for 15 seconds before each mixture check.
NOTE: On Escort/Lynx and Tempo/Topaz, run engine until electric fan comes On.