Spark Plugs - Recommendations/Service
Bulletin: W94-008Section: Warranty
Date: May 24, 1994
Model: ALL
Applicable to: USA/CND
In addition to this document, please refer to Technical Information Bulletin 12/05/94US.
Vehicles built after: Discovery - RA087356
Range Rover - SA644978
Defender - RA942327
All Land Rover products manufactured after the 1st of March, 1994 now have the Champion RN11YCC spark plug (Land Rover part number ERR 3799). This spark plug was originally fitted in the 4.2 liter engine at the start of the 1993 model year and will soon be the only spark plug type available from Land Rover North America, Inc.. The RN11YCC spark plug is a hotter "running" spark plug than the RN9YC. It is safe to use this spark plug on any model/model year of Land Rover vehicles built since 1987.
Land Rover North America, Inc. Parts will soon supersede all previous spark plug part numbers to ERR 3799 (RN11YCC).
In line with the above production part change there are some Warranty Policy, service/maintenance and technical diagnostic issues which require your direct consideration.
Before making any repair or making a warranty claim:
WARRANTY POLICY
Effective May 27, 1994, on vehicles after the VIN numbers listed above:
1) All spark plugs replaced under warranty will be requested for return to LRNA.
2) Land Rover North America, Inc. will debit claims for spark plus on vehicles built after the VIN number given at the beginning of this bulletin if no reproducible fault/defect exists with the spark plug. Please follow the guidelines identified in "Technical Information" to assist you.
3) Land Rover North America, Inc. will not accept any spark plug claim labor or parts (unless the spark plug has a reproducible defect) on any Land Rover vehicles prior to or at PDI.
Vehicles undergo many stop/start type drive cycles between manufacture and delivery to your dealership. It is your responsibility to ensure that your stock and delivery vehicles are maintained. If you suspect a spark plug is "fouled" please follow the procedure outlined in the following technical information on spark plugs.
SERVICE/MAINTENANCE
1) The RN11YCC spark plug is a double copper cored high quality spark plug which is capable of running 30,000 miles without requirement for gaping or cleaning. Please be aware, on vehicles manufactured after the VIN numbers given at the beginning of this bulletin, no 15,000 mile plug maintenance is required. Similarly, customers SHOULD NOT be charged for spark plugs before the 30K maintenance point.
TECHNICAL INFORMATION
Recent and ongoing analysis of spark plug warranty returns has consistently shown that over 90% of warranty returned spark plugs have no defect and at worst suffer from only superficial carbon fouling. Most returned plugs, when subjected to the procedure below all performed satisfactorily although the carboned appearance may have suggested otherwise when the components were removed from the engine they were originally fitted to.
The build-up of carbon deposits can be due to a number of factors such as:
^ Plugs removed immediately after cold start or prolonged idling in the workshop before reaching burn-off temperature.
^ Continuous short drive cycles by customer when the vehicle is operated from cold in stop and go traffic/light low load drive cycles.
^ Excessive oil consumption.
Superficially carbon fouled plugs are not faulty and therefore DO NOT qualify as manufacturers liability.
An engine itself is a good plug cleaner and therefore the plugs are best checked after a short road test at moderate speeds with the engine at normal operating temperature.
Alternatively, with the engine at normal temperature in the workshop hold the engine speed at 2,000-2,500 rpm for 2-3 minutes. This will raise the temperature of the insulator nose and result in some carbon burn-back at the insulator tip.
Spark plugs which suffer from "fuel loading" resulting from no start at temperatures below 0 degrees F can be air dried and re-installed. The plug is not defective and should not be condemned simply because it is fuel logged.
Spark plugs SHOULD NOT be replaced in an attempt to improve idle quality. Other types and brands of plugs may provide a marginal improvement in idle quality when newly installed, as would a new set of ERR3799 (RN11YCC), but none of these options provide any long term improvement.