The J-series V6 engine may have a long history dating back to 1998, but that doesn't mean there aren't a few problems to take note of. Some issues relate to the direct-injection "Y" engines fitted to later Acuras, but the 4th-gen TL only ever had conventional fuel injection, so that's the good news. The bad news is that the Variable Cylinder Management (VCM) system that deactivates certain pistons to run the engine in three-cylinder mode under low loads is prone to causing quite a long list of 2009-2010 Acura TL 3.5 and 3.7 mechanical problems, with the 3.7-liter models being significantly worse than the 3.5. It seems as if the piston rings on the switched-off pistons on the cooler side of the engine are prone to lining up and allowing oil past, which is burnt by the engine, increasing oil consumption. Oil consumption can exceed a quart per 1,000 miles.
To add insult to injury, the mere 4.5-quart oil capacity of the J engine means that oil levels can drop critically low pretty quickly if you don't check your oil level frequently. Low oil levels lead to many problems, including excessive camshaft wear, increased friction, overheating, and, if ignored, eventual engine failure. VCM units' gaskets also tend to fail, which causes oil to leak from the unit, often dripping on the alternator and ruining that part as well; in fact, many 2009-2014 Acura TL alternator problems and replacements are due to this issue. Some owners have resorted to hacking the system to disable VCM, as there's no dashboard switch to do it. Pre-cat failure is also not uncommon, and because the pre-cats sit so close to the engine, fragments of the failing cat can be sucked in by the exhaust valves, seriously damaging the engine. If your exhaust emits a rattling sound, have it checked urgently.
The J engine is also more maintenance-intensive than some rivals' engines because it needs a new cambelt every 50,000 miles or so, although 60,000-mile intervals should suffice under normal conditions. The car's maintenance reminder often notifies owners of the cambelt change too late, so don't exceed the 60,000-mile threshold. This being an interference engine, damage will be extensive if the cambelt fails. Since the water pump is also driven by the cambelt, it is good practice to replace it at the same time. Since the V6 also has no automatic valve-lash adjustment, you have to check valve clearances every 30,000 miles because, once the tell-tale ticking sound of out-of-adjustment valves starts, you have little time before camshaft damage follows. Maintain a J engine religiously and it can take you to 200,000 or even 300,000 miles, but neglect it and you can run into major problems before 150,000 miles.
Mileage:Camshaft wear usually results from lax maintenance and is not mileage-dependent. Adjust the valve clearances every 30,000 miles and replace the cambelt every 50,000-60,000 miles. Oil consumption on the 3.7-liter V6 can become an issue from 47,000-83,000 miles and on the 3.5 from around 150,000 miles.
Cost:Acura extended the warranty for VCM-related problems and excessive oil consumption of up to eight years/125,000 miles, but a used 4th-gen Acura today won't qualify anymore, so you're looking at between $1,700 and $4,000 in repairs, depending on what needs to be done, which is often the replacement of piston-and-rings sets. An entire engine replacement can add up to over $6,500. A cambelt kit with a water pump shouldn't be much more than $250 and fitment should cost around $300.
How to spot:When looking at a used TL, make sure the engine oil is clear and topped up and check for evidence of frequent servicing and oil changes. Ticking sounds should set off the alarm bells; it indicates excessive valve clearances and possibly camshaft damage. Uneven running or misfiring could indicate fouled spark plugs due to excessive oil consumption. VCM oil leaks should be visible in the area near the alternator. Rattling from the exhaust may indicate pre-cat failure.