Engine Controls - Misfire Faults 50, 51, 52 or 53: Overview
Group 12Engine Electrical Systems
Bulletin Number
12 15 96
Woodcliff Lake, NJ
November 1997
Product Engineering
This Service Information bulletin supersedes S.I. 12 15 96 dated February 1996 which should be removed and discarded from your S.I. binder.
**Asterisks are used to identify changes made to this revision.**
SUBJECT:
M44 Misfire Faults 50, 51, 52 or 53
MODEL:
318i, 318ti, and Z3 with M44 (1/96 - 2/97)
Situation:
Customer Complaint that the "Check Engine" lamp is illuminated and:
^ Fault Codes 50, 51, 52 or 53 is set in the Engine Control Module (ECM/DME)
^ Possible complaint of rough idle
Correction:
1. Follow the repair procedure in section A. (Flow Chart)
**2. Reprogram the Engine Control Module using the MODIC or DIS programming version 11.0 or higher (Follow the reprogramming procedure in section C).**
NOTE:
With the release of P11.0 it is no longer necessary to perform a "Manual Determination" in order to carryout this programming update.
After reprogramming the control module the part numbers listed above should be displayed on the DME identification screen as the number for a programmed control module.
**3. If "Smooth Running" measurement (per DIS) which is located in DME diagnosis under "Service Functions" is greater than 3.0 AND the cylinder leakage is greater than 15% - Remove the cylinder head and cut the valve seats (see section B of attachment).
4. If the "Smooth Running" measurement (per DIS) which is located in DME diagnosis under "Service Functions" is greater than 3.0 and the cylinder leakage is less than 15%, the rough running condition is not caused by excessive valve leakage; In this case it is necessary to troubleshoot the engine for possible air-leaks, ignition problems, fuel supply problems,.. .etc.**
NOTE:
Several repair attempts and measurements on engines have shown that cylinder leak-down values above 15% are definitely not caused by high clearances between pistons and cylinders, as long as these values are within specification. No such out of specification clearances have been reported on any engines to date and all attempts to improve the M44 idle quality by replacing piston/block components have failed.