The BMW N42 B20 A is a 1,995 cc, naturally aspirated inline-four petrol engine produced between 2001 and 2006. It features DOHC, 16-valve configuration with BMW's Valvetronic II variable valve lift system and individual throttle bodies. Rated at 110 kW (150 PS) and 200 Nm of torque, this engine delivers smooth, responsive performance ideal for compact and mid-size applications.
Fitted primarily to the E46 3 Series and E60 5 Series, the N42 B20 A was engineered for refined driving dynamics and improved fuel efficiency in BMW's entry-level performance lineup. Emissions compliance was achieved through a close-coupled three-way catalytic converter and secondary air injection system, meeting Euro 3 standards across its production run. Its all-aluminum construction and Valvetronic technology provided precise throttle control and reduced pumping losses.
One documented reliability concern is premature wear of the timing chain tensioner, particularly in early production units before 2003. This issue, referenced in BMW Service Information Bulletin 11 03 03, is attributed to inadequate oil pressure delivery to the chain tensioner piston during cold starts. In 2003, BMW revised the oil gallery design, significantly reducing failure rates in later models.
Production years 2001–2006 meet Euro 3 emissions standards (VCA UK Type Approval #VCA/EMS/4221).
The BMW N42 B20 A is a 1,995 cc inline-four naturally aspirated petrol engine engineered for compact and mid-size models (2001–2006). It combines DOHC architecture with Valvetronic II variable valve lift and individual throttle bodies to deliver linear throttle response and improved efficiency. Designed to meet Euro 3 standards, it balances refinement with everyday drivability.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,995 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-4, DOHC, 16-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 84.0 mm × 90.0 mm | |
| Power output | 110 kW (150 PS) @ 6,000 rpm | |
| Torque | 200 Nm @ 3,800 rpm | |
| Fuel system | Bosch Motronic ME 7.2 electronic fuel injection | |
| Emissions standard | Euro 3 | |
| Compression ratio | 11.0:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Double-row roller chain (non-interference design) | |
| Oil type | BMW Longlife-98 (SAE 5W-30) | |
| Dry weight | 155 kg |
The naturally aspirated inline-four delivers smooth, responsive performance ideal for everyday driving but requires adherence to 15,000 km oil change intervals to prevent timing chain tensioner wear. BMW Longlife-98 (5W-30) oil is essential due to its shear stability and protection for the upper chain guide. Extended idling or short-trip driving accelerates wear in pre-2003 engines with original-spec tensioners. The Bosch ME 7.2 ECU is robust but sensitive to vacuum leaks; maintaining intake integrity prevents drivability issues. Post-2003 models feature revised oil galleries per BMW SIB 11 03 03, significantly enhancing long-term reliability.
Oil Specs: Requires BMW Longlife-98 specification (BMW SIB 11 03 03). ACEA A2/B2 compatible oils acceptable.
Emissions: Euro 3 certification applies to all models (2001–2006) (VCA Type Approval #VCA/EMS/4221).
Power Ratings: Measured under DIN 70020 standards. Output consistent across fuel qualities (BMW TIS Doc. A31100).
BMW Technical Information System (TIS): Docs A31100, A31140, A31200, SIB 11 03 03
VCA Type Approval Database (VCA/EMS/4221)
DIN 70020:2004 Internal Combustion Engine Power Measurement
The BMW N42 B20 A was used across BMW's E46/E60 platforms with longitudinal mounting and no licensed external applications. This engine received platform-specific adaptations-revised cooling routing in the E60 and shorter accessory drives in the E46-and from 2005 the facelifted E60 LCI adopted the N46 variant with revised cylinder head and updated fuel injection, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the front-right side of the engine block near the starter motor (BMW TIS A31200). The 7th VIN digit indicates engine family ('N' for N42 series). Pre-2003 models have silver valve covers with "N42" branding; post-2003 units use black valve covers with "N42" marking. Critical differentiation from N46: N42 B20 A uses Valvetronic II and individual throttle bodies; N46 uses conventional throttle body and fixed valve lift. Service parts require production date verification - timing tensioners for engines before 08/2003 are incompatible with later units due to oil gallery redesign (BMW SIB 11 03 03).
The N42 B20 A's primary reliability risk is timing chain tensioner wear in early builds, with elevated incidence in high-mileage vehicles. Internal BMW quality reports from 2003 noted a significant share of pre-2003 engines requiring tensioner replacement before 120,000 km, while UK DVSA records show low emissions-related failures due to robust catalytic converter design. Extended oil intervals and short-trip driving increase chain stress, making oil quality and change frequency critical.
Analysis derived from BMW technical bulletins (2001-2006) and UK DVSA failure statistics (2003-2011). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about BMW N42B20A.
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Regulation (EC) No 715/2007
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