Crazy, she said the sound went away after the first 30 seconds of each start. HB'* don't do that.

Back on topic, please. Let'* get a code and diagnose further.

Piston slap is the most common cause of an audible engine KNOCK that goes away after a short run time, but these engines don't really have that problem so I would lean more toward lifter noises.

Collapsed/sticky lifters are the most common cause of an audible engine TICK that goes away after a short run time. The cause of sticky lifters is almost always due to lack of maintenance.

When an engine is shut off, some of the cam lobes will stop in the "open valve" position. As the lifter sits with all this valve spring force against it, the inner lifter plunger will bleed the oil off and will collapse into the lifter body. This is normal.

When varnish, sludge, and carbon build in the oiling system from lack of oil changes, it collects between the lifter body and plunger as well as everywhere else. When this build up gets bad enough, it will cause the lifter plunger to stick in its collapsed position for some time after start up. If it gets bad enough, it will make the lifter stick permanently.

I have heard that certain crankcase cleaning chemicals can help to break down and remove the sludge, varnish and carbon and in turn get rid of the sticky lifter condition and the noise it produces. I have also heard that this process of loosening and removing these deposits can cause even more damage.

If the deposits are big enough and plentiful enough, they can clog the oil pump pick-up screen as they are being removed from other engine parts. If the screen plugs it will starve the oil pump and in turn will starve the engine of oil.

Personally, I don't care for any "mechanic in a can" products such as this.

I agree with you on the mechanic in a can. Very few of them are nothing more than a temporary bandaid. The rest are a waste of money.

THIS would make a lot of sense, because my parents are horrible with regular maintenance. And, uhh, how does one scan for codes?

Also willwren, I did what you said- took off the engine cover, started the car, and I couldn't even hear the tapping this time. Bizarre. And annoying

If this may be sticking lifters from infrequent oil changes and varnish buildup, changing the oil to help redissolve some deposits should be the first step. If the oil is anywhere over 2500 miles and 2 -3 months it'* worth a shot in my opinion. Another step is changing the oil after another 1000-1500 miles, earlier if driven only on short drives. And if that'* the case a good 100 mile roundtrip at interstate speeds would do that motor good. A car salesman told me about 2 quick oil changes quieting dirty lifters as we heard a noisy one (3800) go by crossing the street at the dealership...

I wouldn't let any oil change place sell me additves. I'd rely on the softly working additives in the oil to do the cleanup.

That'* gotta be it, apparently the oil wasn't changed for at least 7 months and this car is a daily driver. I just took it in for a change a week ago, but I'm assuming that this is just leftover crud from not being maintenanced for so long. So I guess my parents should get the oil changed again in about 1500 miles, you say?