Fuel System - Part Throttle Sag
84chrysler5 Models1984 Domestic Passenger Cars Equipped With 2.6L Engine & Federal Emissions Package
Subject
Part Throttle Loss of Power (Sag) Cold Drive Sag
Index
FUEL
Date
October 22, 1984
No..
14-50-84
NOTE: THIS SERVICE IS APPLICABLE ONLY TO VEHICLES EQUIPPED WITH CARBURETOR PN MD068740, WHICH CAN BE IDENTIFIED BY THE LAST THREE DIGITS OF THE PART NUMBER (740) STAMPED IN THE METAL CHOKE COVER.
SIMILAR CHANGES ENTERED PRODUCTION WITH CARBURETOR PN MD081509 (IDENTIFIED BY "509" STAMPED ON METAL CHOKE COVER). THIS REPAIR IS NOT APPLICABLE TO VEHICLES WITH THE "509" CARBURETOR.
SYMPTOM/CONDITION
^ Part Throttle Loss of Power (Sag) - Engine will intermittently lose power (sag) while driving at a constant road speed, usually at highway speed, but could also lose power in city traffic.
This condition is usually characterized by having a good idle and wide open throttle, but is substantially weaker because it still lacks primary venturi fuel supply when the loss of part throttle power occurs.
^ Cold Drive Sag - This condition occurs normally on a medium or heavy acceleration which allows actuation of the carburetor secondary.
DIAGNOSIS
To diagnose the cold sag on heavy acceleration the engine should be cold (overnight or at least an 8 hour soak). Start engine and attempt medium to heavy acceleration from stop. If sag is exhibited during initial vehicle movement, perform this service.
It may not be possible to duplicate the part throttle loss of power condition in the service shop area or even during a short road test due to the infrequency of the occurrence.
PARTS REQUIRED
DRIVEABILITY PACKAGE PN 4342903
Consists of:
1 - Primary Jet Block & Gasket Package PN MD082907
1 - Float Chamber Cover Gasket PN MD608639
1 - Carburetor Flange Gasket PN MD025344
1 - Choke Cover Screw Kit PN MD606977
1 - Thermo Valve (3-port) PN MD081274
1 - Thermo Valve Vacuum Hose Harness PN MD084688
Must be ordered separately:
1 - Authorized Modification Label PN 4275086
REPAIR PROCEDURE
1. Remove carburetor air cleaner crossover.
2. Drain and save approximately one gallon of coolant.
3. To prepare carburetor for removal, disconnect vacuum hoses, canister lines, throttle linkage, return spring and, when so equipped, cruise control cable and bracket, water inlet hose, and 10 mm nut next to sub-EGR valve linkage.
NOTE: IT IS RECOMMENDED BEFORE REMOVING CARBURETOR FROM MANIFOLD THAT THE SIX (6) AIR HORN SCREWS BE LOOSENED USING A HAND IMPACT TOOL WITH A #2 PHILLIPS BIT, A RACHET WRENCH, OR A #2 PHILLIPS SCREWDRIVER BY LIGHTLY TAPPING WITH A HAMMER ON THE END OF THE SCREWDRIVER. (DO NOT REMOVE SCREWS AT THIS TIME, JUST LOOSEN THEM.)
4. Remove the four (4) hold-down bolts that pass through carburetor, then remove carburetor for disassembly.
5. For carburetor disassembly, follow procedures in the service manual.
CAUTION: WHEN SEPARATING THE AIR HORN FROM MAIN BODY, DO NOT PRY ON ANY SOLENOIDS.
FIGURE 1:
FIGURE 2:
6. With air horn assembly inverted on bench, remove primary jet block (note cast "P" on side of block), install replacement (Figure 1), and transfer primary main jet from removed block to replacement. Use new gasket supplied in jet block package (Figure 2).
7. Reassemble carburetor using new Bowl Cover Gasket, PN MD608639, and install on vehicle. Use five (5) new Break-Off Type Screw, PN MD606977, to reinstall choke cover assembly. Use new Carburetor Flange-to-Intake Manifold Gasket, PN MD025344, and install carburetor.
8. Remove coolant temperature sensor to gain access to thermo valve.
9. Locate thermo valve. This valve controls secondary EGR valve operation and canister purge. Disconnect vacuum hoses. Remove and discard valve and install 3- Port Thermo Valve, PN MD081274 in its place.
10. Remove and discard existing carburetor secondary chamber hose.
FIGURE 3:
11. Install new Vacuum Harness, PN MD084688, to 3-port thermo valve, carburetor secondary diaphragm, and diaphragm nipple on carbureted base. Connect two original thermo valve vacuum hoses to 3-port connector as shown in Figure 3.
Special care should be used in routing hoses to insure against crimping or kinks. Trim excess hose if necessary.
12. Reinstall coolant drained in Step 2. Start engine and check for leaks and allow to fully warm up.
13. Check curb idle rpm, readjust if necessary.
FIGURE 4:
14. Type an Authorized Modification Label, PN 4275086, as shown in Figure 4.
POLICY: Reimbursable within the provisions of the warranty
TIME ALLOWANCE:
Labor Operation No. 14-50-84-90 . . . . . . . . . . . . . . . . . . . . . 1.5 Hrs.
FAILURE CODE: AM - Authorized Modification