EGR/Canister Purge - Rough Idle/Hesitation

86chrysler6

Models


1986 2.2L & 2.5L Throttle Body Injected Engines (Not Turbo)


Subject

Rough Idle, Hesitation


Index

DRIVEABILITY


Date May 19, 1986


No.

18-22-86
SYMPTOM/CONDITION

An unstable rough idle during warm up and also when the engine is at normal operating temperatures.

DIAGNOSIS

This condition may be caused by mis-routing of the throttle body vacuum harness. Specifically, the EGR vacuum hose and the heated air door/canister purge hose connections may have been reversed.

REPAIR PROCEDURE

If the hoses are reversed, the EGR valve, heated air door, and the charcoal canister purge systems will not operate properly. Canister purge and EGR may be operational at closed throttle idle, which will cause rough idle and off idle hesitations.

FIGURE 1:

Inspection of Vacuum Harness Connections

1. Remove air cleaner housing.

2. Inspect the rear of the throttle body to insure the EGR vacuum line is connected to the top most nipple. The EGR nipple is located above the brake booster hose. Also be positive the right angle boot on the nylon vacuum harness for the heated air door and canister purge signal is connected to the lower most nipple on the throttle body. Correct vacuum hose routings are illustrated in Figure 1.
3. When the vacuum hose routings are correct as illustrated, check for vacuum leaks at:

a. EGR tube-to-intake manifold connection.
b. Power brake booster.
c. Speed control system.
d. Fender mounted vapor canister signal line and solenoid.

FIGURE 2:

4. If there are no vacuum leaks and the engine still idles rough, replace the logic module. It is imperative that no vacuum leaks exist prior to logic module replacement. Replacing the logic module on an engine that has improperly routed vacuum hoses or vacuum leaks will not solve this condition.

Proper applications and part numbers for the logic modules are illustrated in Figure 2.

FIGURE 3:

5. If the logic module is changed, an Authorized Modification Label, PN 4275086 (Figure 3), must be imprinted and attached near the original VECI label.
TIME ALLOWANCE: Refer to existing Labor Operation Time Schedule for operation and time.