BMW Repair: 2002 318se vin KJ84073, valve lifters, fuel vapors

Question
Hi Evan,
I recently noticed my 2002 318SE has a loud ticking noise at idle.It goes as soon as revs increase.The oil level is at max and I have no warning lights or errors reported.The car has only done 34000 miles .
Otherwise the car behaves fine.Any ideas as to what it could be,if it is serious or just an annoyance? And any possible repairs which don't involve selling a kidney to pay for.
Thanks in advance.

Answer
Gareth, most ticking noises at idle are usually mistaken for the purge valve opening regulating fuel vapors from the gas tank into the engine (normal operation) or it could be a faulty hydraulic valve lifter. Valve lifters when noisy are not filling up with oil or are bleeding oil off too fast, causing them not to take up the valvetrain clearance as designed. Most or the time it is just an annoyance, but can become bad enough too allow the valves not open completely and cause a rough running or misfire. Not a cheap item to remedy because the cylinder head valvetrain has to come apart to replace the faulty HVA (hydraulic valve actuator/lifter). Have it diagnosed professionally because I can't hear noises over the internet.
-Evan