Majestic L6-4.0L (1990)
Camshaft: All Technical Service Bulletins
Engine - Poor Idle Quality
12-57
Poor Idle Quality - Normally Aspirated AJ16 Engine - Valve Timing Modification
MODEL: 4.0L Normally Aspirated 1995 MY
DATE: 8/95
Engine numbers listed below
ISSUE:
To improve idle quality, revised camshafts with reduced valve timing overlap were introduced on the normally aspirated engines as running change
95/13.
The original camshafts, with a maximum opening position of 110 degrees have been superseded by camshafts with a maximum opening position of 114
degrees. This change is accomplished by machining the camshaft slot in a different position. The valve timing overlap is reduced from 22 degrees on the
110 camshafts to 14 degrees on the 114 camshafts, Illustration 1.
The maximum opening position of the 114 intake camshaft is 114 degrees after top dead center (ATDC) while the maximum opening position of the
exhaust camshaft is 114 degrees before top dead center (BTDC).
Normally aspirated engines with the 110 camshafts, that exhibit poor idle quality, can be modified to achieve the same reduction in valve timing overlap
as with the 114 camshafts.
NOTE:
Refer to Illustration 5, to identify engines with 110 camshafts that have already been modified.
The 114 camshafts were introduced for a period, withdrawn, and then reintroduced as a permanent change.
The table lists the change points by engine number:
ACTION:
In case of a customer complaint of poor idle quality on a vehicle equipped with the 110 camshafts only, first check for punch marks on the timing cover
near the camshaft position sensor, Illustration 5, to determine if the timing modification has already been performed. If not, reset the camshaft timing and
