Engine - Detonation at High MAP, High RPM Operation
Bulletin No. T 86-66File in Group 6E
Number 31
Corp. Ref. No. 616505
Date June '86
SUBJECT: DETONATION AT HIGH MAP, HIGH RPM OPERATION
MODELS AFFECTED: 1996 DE VILLE/FLEETWOOD, LIMOUSINE AND COMMERCIAL CHASSIS (FEDERAL AND CALIFORNIA EMISSION SYSTEMS) EXCEPT TOURING COUPE/SEDAN
Some 1986 front-wheel-drive De Ville/Fleetwood, Limousine, and commercial chassis vehicles may experience detonation at high RPM and high MAP conditions. Vehicles built after VIN 249254 are equipped with a new PROM to correct this condition. The new PROM supersedes previous service PROM part numbers for PROM I.D.s 253/261/254. The new PROMs have revised spark calibration for the following ranges of MAP and RPM:
RPM MAP
3200 - 4000 Above 82 kPa
4000 - 4800 Above 72 kPa
The new PROM's can be installed in all 1986 Federal and California De Ville/Fleetwood, (except "Touring" engine) Limousine and commercial chassis. For vehicles built before VIN 249254, the new service PROM part numbers will repair detonation or detonation related conditions that occur in the above MAP and RPM ranges.
Since a number of basic engine mechanical conditions can cause detonation, the cause of the detonation symptom must be corrected to assure proper operation of the vehicle under all conditions. Any detonation condition that does not occur in the above MAP and RPM range should be repaired using the "Symptom" diagnosis as provided in Section 6E, Subsection B in the 1986 De Ville/Fleetwood Service Information Manual before replacing a PROM.
When ordering, use the following part numbers to obtain the new PROM:
Supersedes
Emission Service
Vehicle System Part Number PROM ID P/N PROM ID
DeVille/Fleetwood Federal 16059149 255 16053039 253
DeVille/Fleetwood California 16059167 262 16053003 261
Limousine/Commercial Fed/Cal 16059163 256 16053022 254
Chassis
For warranty purposes, use labor operation J6364 at .5 hours.