BMW 320i (E90) engine: which one, problems and replacement

The BMW 320i in the fifth 3 Series saloon generation (E90, built 2005–2012) was built with one engine, the N43B20: a 2.0 L petrol inline-4 with 170 hp.

This guide tells you which engine your 320i has, what goes wrong with it, what a replacement costs from our stock and what else to plan for when you fit one.

• Generation: fifth 3 Series saloon, 2005–2012
• Body styles: E90 (saloon)
• Engines: N43B20
• Output: 170 hp
• Replacement engines in stock: ask the desk for the next arrival

Which engine is in your 320i?

N43B20 in the 320i

The N43B20 was used in the E90 320i, built 2007–2011. It is a 2.0 L naturally aspirated petrol inline-4 with 170 hp and 210 Nm.

Reading the code: N marks an N-series code, the generation of BMW engines introduced from 2001; 43 is the family number; B stands for petrol (from the German Benzin); 20 is the capacity in decilitres, so 2.0 litres.

320i engines by model year

The 320i kept the same engine for the whole E90 run, which makes ordering simple: any unit with the same code fits, subject to the gearbox, drive type and sump.

Other cars with the same engine as the 320i

A replacement engine does not have to come from another 320i. These models left the factory with the same engine code, so a unit from any of them is a candidate donor once the sump, mounts and ancillaries are matched to your car.

N43B20: BMW E81 120i, BMW E60 520i.

How to confirm your engine code

The 320i only used the N43B20, but the exact version can still change with the build date, gearbox and market. Send us the last seven characters of the VIN and we read the engine code from BMW's records, or look for the code stamped on the block. How to find your BMW engine code.

Known 320i engine problems

The N43B20 in the 320i shares the known weak points of the N43 family. Full N43 guide.

Piezo injectors. Injectors leak or misfire, especially with poor fuel.

Ignition coils and spark plugs. Lean-burn combustion is hard on coils and plugs; misfires are common.

NOx sensor and catalyst. The NOx storage catalyst and sensor degrade, especially with high-sulphur fuel.

Timing chain. Chain stretch occurs at higher mileage.

Vacuum pump and oil leaks. Like the N46, the vacuum pump and valve cover leak.

Symptoms to watch for on the 320i

Rattle for a few seconds after a cold start. The classic sign of a weak timing chain tensioner or stretched chain. It must be checked quickly: a chain that jumps a tooth can bend valves.

Poor low-down torque and uneven idle. VANOS seals or solenoids. The engine may run well at high revs but feel flat and lumpy at low speed.

Long cranking before the engine starts. On direct-injection engines, a weak high-pressure fuel pump or leaking injector lets pressure drop when the engine is off.

Looking after the 320i engine

• Oil: 5W-30 BMW Longlife-01 or Longlife-04, about 4.25 litres.
• Service interval: Oil every 15,000 km; spark plugs every 60,000 km.
• Timing drive: Timing chain at the front.
• Workshop notes: Use good-quality, low-sulphur petrol. Fit new coils and plugs to a used N43 before first start.

Buying a used engine for the 320i: checklist

1. Warranty terms in writing. Read what the warranty covers, how long it runs and what fitting conditions apply. Most warranties require a qualified workshop, new fluids and filters, and replacement of the cooling parts that caused the original failure.
2. Look at the oil and coolant. Clean oil without metal particles and coolant without oil are good signs. Milky oil, oily coolant or a burnt smell mean the engine needs further checks before it is fitted.
3. Confirm the exact engine code. Read the code stamped on the block and compare it with the code for your car. Send us the last seven characters of the VIN and we confirm the match before anything is paid.
4. List of what is fitted. Engines are sold with different ancillaries: some have the turbo, injectors, manifolds, alternator and starter, others are long blocks. Agree the list in writing so you know which parts must come from your old engine.
5. Sump, oil pickup and drive variants. Rear-drive, xDrive and front-drive cars can use different sumps, oil pickups and engine mounts even with the same engine code. Check that the sump matches your subframe and front axle.
6. Timing chain noise. Listen for a rattle at the front of the engine for the first seconds after a cold start. On an engine that cannot be run, look at the chain guides through the oil filler or with the valve cover off.
7. VANOS operation. Rough idle, a rattle from the front of the head and a loss of torque at low revs point to VANOS seals or solenoids. These are serviceable parts and are easier to renew with the engine out.
8. Double VANOS units and solenoids. Ask for the adaptation values or fault history if the engine was running. Solenoids are inexpensive and are often replaced as a matter of course on a used engine.
9. Injectors and high-pressure fuel pump. Direct-injection engines rely on high-pressure pumps and precise injectors. Ask whether the injectors are original or updated and whether there were fuel pressure faults.

BMW 320i replacement engine cost

We do not have a 320i engine on the shelf at the moment. Send us your VIN or the code you need and the desk will tell you when the next unit arrives and what it will cost.

On top of the engine, budget for the workshop's labour and the parts that are best replaced while the engine is out: engine mounts, the rear main seal, cooling parts, a clutch or converter seal, fluids and filters.

Will it fit my 320i?

Will the N43B20 fit my BMW E90 320i?

Yes, the BMW E90 320i left the factory with the N43B20, so an N43B20 from another car is the direct replacement. The fifth 3 Series saloon was built 2005–2012, and the N43B20 was produced 2007–2011, so check that your car's build date falls inside that window. Confirm the drive type (rear-drive or xDrive), the gearbox (manual or automatic) and the emissions standard, because these can change the sump, the flywheel and the software. Send us the VIN and we check all of it for you.

How much is a replacement engine for a BMW E90 320i?

We do not have an N43B20 on the shelf for the E90 320i at the moment. Units arrive regularly; send us your VIN and we will tell you when the next one is ready and what it will cost, including delivery.

Engine swaps and upgrades for the 320i

These engines were fitted to other versions of the E90 at the factory, which makes them the most practical upgrades: the body was designed around them and many parts are shared.

Can I fit the N45B20S in my 320i?

Yes, it is one of the more common upgrades. Both are petrol inline-4 engines, so the mounting points are similar, but the N45B20S needs its own wiring and engine control unit, the matching gearbox or clutch, and often a different sump, cooling and exhaust. The gain is 3 hp and 0 Nm. In Germany and most of Europe an engine swap must be inspected and registered.

Can I fit the N47D20 in my 320i?

It is a full conversion: the N47D20 runs on diesel and the N43B20 on petrol, so the fuel system, wiring, engine control unit, instrument coding and usually the gearbox change too. The gain is 14 hp and 170 Nm. In Germany and most of Europe an engine swap must be inspected and registered.

Can I fit the N47D20D in my 320i?

It is a full conversion: the N47D20D runs on diesel and the N43B20 on petrol, so the fuel system, wiring, engine control unit, instrument coding and usually the gearbox change too. The gain is 14 hp and 170 Nm. In Germany and most of Europe an engine swap must be inspected and registered.

Fitting a replacement engine in the 320i

1. Inspect or replace the timing chain parts. Look at the guides and tensioner. On high-mileage engines, replacing them now costs far less than doing it later.
2. Reset VANOS adaptations. Clear the VANOS adaptations so the ECU learns the camshaft positions of the new engine.
3. Fill with the right oil and prime it. Fill with new oil of the correct specification and a new filter. Crank with the fuel and ignition disabled until oil pressure builds.
4. Coding and adaptations. On modern BMWs, the engine ECU must be matched to the car's immobiliser (CAS, FEM or BDC). Reset adaptations, register the battery and clear faults with diagnostic software.
5. First start and leak check. Start the engine, let it idle and watch oil pressure, temperature and fault codes. Check for leaks and bleed the cooling system.
6. First 1,000 km. Drive gently for the first few hundred kilometres, vary the engine speed and avoid full load. Change the oil and filter after about 1,000 km to remove any assembly debris.

The full fitting and first-start procedure.

320i engine questions

How much is a replacement N43B20 engine for a BMW E90 318i?

A used N43B20 for the BMW E90 318i costs from about 1.050 € to 1.850 € in our yard. The price depends on the year, the mileage and the parts that come with the engine.

Shipping is a flat 249 € per order. It is added once at checkout and printed on the invoice, so there is no extra fee later. Inside the EU there is no import duty. Outside the EU, the receiver pays local duty and VAT.

A replacement engine is often much cheaper than rebuilding a damaged one, and much faster. The N43B20 you buy is photographed and checked in Hamburg before it is listed.

Eligible engines come with a 12 months warranty from the delivery date. It covers internal mechanical failure under normal use and correct fitting by a qualified mechanic or workshop. Not sure? Send us your VIN and your gearbox code. We match the engine family, the year window and the parts on the engine before anything is reserved, and the check is free.

See all N43 Engines · Search N43B20 in the shop

Which cars use the BMW N43B20 engine?

BMW fitted the N43B20 to the BMW E87 118i, BMW E90 318i and BMW E81 120i. These cars were built with this engine from about 2007 to 2011.

The badge on the boot is not enough to be sure. The same model name can hide two different engines, for example after a facelift or a change in emission rules. Always read the engine code stamped on the block, or look it up with your VIN.

The N43B20 is the only N43 version we list, which makes it easy to pick, but the wiring and the engine computer still need to match your car.

Not sure? Send us your VIN and your gearbox code. We match the engine family, the year window and the parts on the engine before anything is reserved, and the check is free.

See all N43 Engines · Search N43B20 in the shop

How much is a replacement N43B20 engine for a BMW E81 120i?

A used N43B20 for the BMW E81 120i costs from about 1.050 € to 1.850 € in our yard. The price depends on the year, the mileage and the parts that come with the engine.

Shipping is a flat 249 € per order. It is added once at checkout and printed on the invoice, so there is no extra fee later. Inside the EU there is no import duty. Outside the EU, the receiver pays local duty and VAT.

A replacement engine is often much cheaper than rebuilding a damaged one, and much faster. The N43B20 you buy is photographed and checked in Hamburg before it is listed.

Eligible engines come with a 12 months warranty from the delivery date. It covers internal mechanical failure under normal use and correct fitting by a qualified mechanic or workshop. Not sure? Send us your VIN and your gearbox code. We match the engine family, the year window and the parts on the engine before anything is reserved, and the check is free.

See all N43 Engines · Search N43B20 in the shop

How much does a used BMW N43B20 engine cost?

A used BMW N43B20 engine in our yard usually costs between 1.050 € and 1.850 €. The exact price depends on the year, the mileage and the parts that come with the engine.

Our units show recorded mileage from about 22,000 km up to around 200,000 km. Lower mileage and more ancillaries mean a higher price. Each listing shows its own price, and the price you see is the price you pay. Prices include VAT for private buyers.

Shipping is a flat 249 € per order. It is added once at checkout and printed on the invoice, so there is no extra fee later. If you order a gearbox or a second engine on the same order, the fee is still charged once.

Inside the EU there is no import duty. For the UK and other non-EU countries, import duty and local VAT are paid by the receiver, and we supply a commercial invoice.

See all N43 Engines · Search N43B20 in the shop

Delivery, warranty and payment

Before a 320i engine leaves our Hamburg yard it is drained of oil and coolant, every opening is sealed, and it is strapped to a pallet and wrapped. We send photographs of the packed unit and the tracking details.

Door-to-door delivery is included to the address you give at checkout. Typical delivery takes three to five working days within Germany and neighbouring countries and five to ten working days to the rest of Europe and the UK.

Every engine carries a 12-month warranty on eligible internal failure when a qualified workshop fits it with new fluids and filters. Payment is by card, bank transfer or crypto; your invoice is emailed as soon as you order.

All E90 engines · N43 engine guide · BMW 320i engines for sale · Send us your VIN