P0014 fault code.

In these engines the oil pump is adjustable, and the factory setting deliberately keeps the oil pressure low at low revs to reduce the drag of driving it. At low revs the stock pump works at around 1.8 bar, up to 2 bar at most. With a warm engine at idle this can fall further, and values below 1 bar have been reported. The camshaft adjusters feel the low pressure first, because the oil pressure itself is what holds the adjuster in place: this is where the clacking noise heard at idle comes from. The chain tensioner follows, which the same pressure tensions, and the timing chain therefore wears faster. The reference values for this engine family are 2 bar at idle, 3 bar at 2,000 rpm and 4.5 bar at 4,000 rpm. The turbocharger and the camshaft are lubricated from the same circuit. A strengthened oil pump raises the idle pressure by about 20 per cent. Repairing the pump costs between 800 and 2,800 euro, and replacing a worn chain is a further 1,200 to 3,500 euro.

The 1.6 naturally aspirated petrol engines of the Astra H (Z16XEP, Z16XE1, Z16XER) run a timing belt, not a chain. The replacement interval is 150,000 km or 10 years, whichever comes first.

VANOS adjusts the position of the camshaft with the pressure of the engine oil, and a solenoid valve metres that pressure. The valve sits in the oil circuit, and a fine filter screen protects the spool inside it from larger particles. That screen clogs with carbon and deposits: less oil flows through, and VANOS then adjusts late or does not move at all. The symptoms are a rough idle, rough running, a lack of torque at low revs and higher fuel consumption, because the valve timing is off. A short metallic clacking can also come on a cold start and goes quiet after 10 to 20 seconds. The engine warning light comes on with a camshaft fault code, and depending on the severity the engine control unit switches to limp mode. The fault code narrows down the cause. P0010 and P0013 typically mean the solenoid valve itself, that is a circuit fault or reduced oil flow through the clogged screen. P0011 and P0014 point more to a mechanical cause: a stretched timing chain or a worn adjuster. P0012 and P0015 report late camshaft control, whose common cause is slow pressure build-up at the adjuster, so again the dirty valve. The valve itself is a small part, between 50 and 120 euro, and with a clean screen cleaning is often enough; replacing the whole adjuster, by contrast, is a four-figure job. The reported repairs ran between 80 and 1,200 euro, depending on whether cleaning is enough and how many valves are affected. The main cause of the screen clogging is a stretched oil change interval and carbon-laden oil.