Engine - Miss/Surge/Chuggle at Highway Speeds
File in Group: 6Number: 6
Corp.Ref. No.: 316005
Date: June, 1993
SUBJECT:
INTERMITTENT MISS/SURGE/CHUGGLE AT HIGHWAY SPEEDS
MODELS AFFECTED:
1993 ELDORADOS, SEVILLES, AND ALLANTES EQUIPPED WITH NORTHSTAR ENGINES
Some 1993 Eldorados, Sevilles, and Allantes equipped with Northstar engines may experience an intermittent miss/surge/chuggle condition that is most apparent at highway speeds (1100-1900 rpm) under a load or light to moderate acceleration. Condition could also occur at 20-40 mph speeds but under the same engine rpm as noted above. Condition typically occurs with no PCM codes set.
This condition may occur due to the ignition system resynchronizing under high spark loads because of noise induced into the sensor (crank/cam) circuits and/or the ignition control module (ICM). The noise may be transmitted from a bent or damaged terminal in the ICM or harness connectors. In addition, the noise may be occurring due to spark plug wire(s) contacting the ICM (particularly the number 1 wire). Refer to Figure 1.
To repair this condition use the following procedure:
1. Diagnose and repair all PCM trouble codes first.
2. Check (G102 for Eldorado and Seville) or (G104 for Allante), located on the engine block near the transaxle case extension, for being clean and tight. Refer to Service Information Manual Electrical Diagnosis - Section 8A-201 for an illustration of the area.
3. Disconnect all four ICM electrical connectors and inspect for bent or damaged terminals in the ICM or harness connectors.
4. Remove and reinstall the rear (RH) bank spark plug wire boots so that the wires exit the boot away from the ICM Assembly. This will prevent the wires from contacting the ICM Assembly (particularly the number 1 wire). Figure 1 illustrates the incorrect way for spark plug wire routing. Figure 2 illustrates the correct way for spark plug wire routing.
For warranty purposes use Labor Operation T6724 at .5 hour.