Common BMW N43 Engine Problems: Causes, Consequences, Solutions

By Nick Marchenko, PhD

The BMW N43 is a four-cylinder gasoline engine introduced in 2001. Its debut was celebrated in the 1-series E87 and 5-series E60, later also in the 3-series E90. In comparison to its predecessor, the N42, a shift from intake manifold injection to direct gasoline injection was made for the purpose of performance and fuel consumption optimization, and the Valvetronic was also omitted.

BMW N43 Engine Problems

With the removal of the Valvetronic, one weak point was eliminated; however, several new issues have arisen due to the shift to direct gasoline injection. Oil loss and elongated timing chains are still significant concerns. Below we address the common weak points of the N43.

Stretched Timing Chain

The timing chain of the N43 is known to stretch prematurely, usually resulting in catastrophic engine damage. This is often due to a defective chain tensioner, where the wear is accelerated by late or missed oil changes. Although an updated version of the chain tensioner with part number 11318685091 has been available since October 2016, the weak point is only somewhat alleviated.

During vehicle inspection, attention must be paid to clacking or rattling noises during engine start (preferably cold) and load changes. If this occurs, the chain is likely already elongated, and engine damage may be imminent.

Defective NOx Sensor

Due to lean operation with stratified charging, large amounts of nitrogen oxides are emitted, necessitating the use of a NOx storage catalyst. Generally, this isn’t problematic, but the NOx sensor often is. A defect usually announces itself with increased fuel consumption since the engine no longer operates in lean mode.

Faulty Ignition Coils

Problems with the ignition coils may occur in N43 engine vehicles from the production years 2007 and 2008. Since the ignition coils were replaced free of charge during a service campaign, this issue is likely to appear only rarely.

Defective High-Pressure Fuel Pump

The high-pressure fuel pump in the N43 often poses problems. If the engine's cold start is long delayed or if jolts are felt under full load, this indicates a defect in the high-pressure fuel pump.

High Oil Loss / Oil Consumption

The N43, like many other older BMW engines, can have high oil loss or oil consumption. The following areas are most frequently affected:

• Valve cover gasket
• Crankcase ventilation (integrated into the valve cover)
• Vacuum pump

Faulty VANOS Solenoids

The VANOS solenoids will suffer a defect sooner or later. A defect is particularly noticeable in the lower rpm range by rpm fluctuations and noticeable loss of power; occasionally, there may also be difficulties starting.

Carbon Formation in the Intake Tract and Valves

With direct gasoline injection, the N43 will struggle with coked injectors and carbon deposits in the intake tract. To delay the resulting problems (loss of power, higher consumption, etc.), it is advisable to use cleaning fuel additives regularly when refueling.

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Conclusion

The never-ending issue with the timing chain plagues the N43 just as much as its predecessors. Additionally, new problems have arisen due to the switch to direct injection. A BMW with this engine should not be purchased blindly.

Nick Marchenko, PhD

Industrial Engineer & Automotive Content Specialist

Nick writes in-depth guides on car clubs, engine specs, vehicle ownership, and modifications, combining engineering knowledge with automotive passion.

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