Engines · BMW
BMW N46 2.0 petrol common problems
The N46 is BMW's four-cylinder petrol in 1.8 and 2.0 forms, with Valvetronic variable valve lift and twin balance shafts, built from 2004 to replace the N42. It powered the 316i, 318i, 320i, 118i, 120i, X1 18i and Z4 2.0i, and from 2007 the N43 took over in many markets, including the UK, while the N46 continued in others.
Common problems and what to look for on the N46
The known issues most worth checking when you view a car with this engine. None of them means a car is a bad buy, but they're worth knowing about before you buy, and a good history often shows they've been dealt with.
Timing chain and guide wear
What to look for: Ask for the engine to be started from stone cold with the bonnet open, and listen at the front of the engine. It should settle to an even idle within a couple of seconds. A metallic rattle that lasts longer than that, or comes back as the revs drop, is the thing to note. Ask for any invoice for timing chain work.
Why it matters: The chain stretches and its plastic tensioner rails and guides wear with mileage. Specialists advise replacing the timing chain assembly by about 100,000 miles. A car with that invoice is in a good position, and regular oil changes slow the wear.
Oil leaks
What to look for: With a torch, look around the top and front of the engine and underneath for wet oil or fresh drips. Check for a burning oil smell after the drive.
Why it matters: BMW's four-cylinder petrols of this era are known for oil leaks as gaskets and seals harden with age. Leaks are routine fixes for a specialist, and an oil-tight engine is a good sign that it's been looked after.
Valvetronic motor and sensor
What to look for: Note any rough idle, hesitation, loss of power or engine management light on the drive. Ask whether the fault codes have been read recently and whether the Valvetronic motor or sensor has been replaced.
Why it matters: Valvetronic varies how far the inlet valves open, in place of a conventional throttle, using an electric motor and a position sensor. Either can fail with age, causing rough running and warning lights. A code reader points to the part, and replacing it restores the running.
More known issues, covered in the full guide for each car
- VANOS wear
Cars with the N46
- BMW 3 Series E46: Later 316i and 318i (earlier cars have the N42)
- BMW 1 Series E81/E82/E87/E88: 118i and 120i, to late 2007
- BMW 3 Series E90/E91/E92/E93: 318i and 320i, to 2007 in the UK
- BMW X1 E84: sDrive18i and xDrive18i
- BMW Z4 E85 and E86: 2.0i (150PS)
A pre-purchase inspection guide for your car
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General points for the engine, last checked October 2026. Every car is different, so treat this as a guide to what to look at, not a verdict on any car. CrankSight is independent and has no connection with any manufacturer.