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Found this on e90fanatics board - might be related to the idle issue... still studying availble info...
SIB 13 01 07
SUBJECT
Fuel Injection and Induction System Cleaning
SITUATION
Deposits found in the injection and induction system may cause the vehicle to experience a variety of drivability complaints, eventually leading to the Service Engine Soon Lamp to be illuminated. Some of the possibilities are listed below.
Fuel Injectors
Deposits at the fuel injector's tip can impact fuel flow, disturbing the air/fuel mixture ratio.
Symptoms are the following: Hesitation or stumble during acceleration or even loss of power; poor fuel efficiency; increased emissions of HC and CO; and "Service Engine Soon" light illumination due to misfire faults, or lean mixture adaptations.
Intake Valves
Deposits at the valves and on the intake manifold ports can absorb fuel during the warm-up phase, leaning out the air/fuel mixture ratio. Carbon build up may disturb the mixture flow at low throttle conditions and/or idle speeds.
Symptoms are the following: Poor drivability; loss of power; unstable and/or rough idle; increased emissions of HC, CO and NOx; and "Service Engine Soon" light illumination due to intermittent misfire faults.
Combustion Chamber
Combustion Chamber Deposit Interference (CCDI) occurs when there is contact between carbon deposits on the piston crown and the cylinder head. The noise can be confused or misdiagnosed as a ping, knock or other noises that could indicate a mechanical failure. CCDI occurs first as a cold start noise that can fade as the engine warms to operating temperature. The noise will reoccur at the next cold start. As deposits build, there is an increase in compression temperature that may cause pre-ignition detonations.
Symptoms are the following: Knocking; pinging; run-on; poor acceleration; octane requirement increase; increased emissions of NOx; and engine idle speed surges.
Depending on the manufacturer, fuels may contain various additives such as: oxidation and corrosion inhibitors; metal deactivators; emulsifiers; and anti-icing agents and dyes. In addition, they are required to include some form of an intake system deposit control package. Unfortunately, not all fuels are created equal, and some additive packages are not effective enough to maintain the integrity of the intake systems in high performance engines, or engines operating under severe environmental conditions. Even worse, the intake system deposit control additives in some fuels may actually contribute to the combustion chamber deposits accumulation and to the problems associated with those deposits, i.e., knock, run-on and increased emissions of oxides of nitrogen.
To remedy these complaints, the BMW Group has developed a new special tool and cleaner concentrate to clean the fuel injectors, induction system and combustion chamber of harmful deposits.
NOTE: This tool is designed to be used with low pressure fuel injection systems. This material or tool should not be applied to a vehicle utilizing the High Pressure Injection System.
Refer to the attached procedures described below by model. It is recommended that two applications be made consecutively on each vehicle. If more applications are required, please contact the Technical Hotline via PuMA.
Procedure A – All vehicles equipped with the M54, N52, N51 and N52K engines
Procedure B – All vehicles equipped with the M56 (SULEV) engine
Procedure C – All vehicles equipped with the N62, N62TU and S85 engines
Procedure D – All vehicles equipped with S54 engine
IMPORTANT: Before starting the cleaning procedure, place the vehicle in a well-ventilated area. If the cleaning procedure occurs indoors, be sure to have the vehicle connected to an exhaust removal system. It is necessary to wear Nitrile rubber gloves and safety glasses during this procedure.
The shop air supply should be dried using a general purpose filtering system; the tool is not recommended for use with a lubricating system.
FINAL PROCEDURE FOR RELEASING THE VEHICLE TO THE CUSTOMER
Advise the customer that it is necessary to add one bottle of BMW Group Fuel System Cleaner Plus PN 82 14 0 413 341 with either TOP TIER Detergent Gasoline or Premium Fuel, with a minimum octane rating of AKI 91, the next time that the vehicle is refueled.
For optimum cleaning, advise the customer to add one bottle every 3,000 miles when refueling. Refer to SI B13 05 06 BMW Fuel System Cleaner Plus.
More related information regarding fuel systems and fuel additives can be found in the following Service Information Bulletins:
SI B13 01 06 Alcohol Fuel Blends in BMW Vehicles
SI B13 02 06 TOP TIER Detergent Gasoline in BMW Vehicles
SI B13 04 06 Alcohol Detection Procedure
SI B13 07 06 Gasoline Quality & Detergent Additives – Customer Information Brochure
WARRANTY INFORMATION
Because carbon deposit build up is related to fuel quality, it cannot be considered a defect in a vehicle's materials or workmanship. Consequently, performing the BMW Group Fuel Injection & Induction System Cleaning Procedure is not covered under the terms of the BMW New Vehicle Limited Warranty or maintenance plan.
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