What is that diesel sound coming from your gas 3.2V6 Isuzu Rodeo engine?

== == == == Low octane fuel will cause this. Run a tank of high octane (PREMIUM) through it or add a bottle of octane boost in a full tank and it should go away. I have a 95.5 Honda Passport with 3.2 V6. I tried the higher octane method and to no help to my problem. switched to mobil 1 synthetic 5w/20 as recommended by everyone who has had this problem- has helped some- still a low tap sound (apparently this is an inherited problem with this engine- the oil return ports are too small and if the gather any trash/gunk- can become clogged and cause the tapping sound- I do an engine oil flush with every oil change). I will be replacing my timing belt later this week- its been stated that the sound could be timing belt slapping. engine is strong- runs good- have 211,000 miles on it- the tap started about 160,000 miles. It think its way overdue for that timing belt. updated a week later: replaced timing belt (bando brand- factory OEM part) (note- timing belt was worn - considerable amount of slack in belt= hence belt slapping the belt cover and causing a ticking sound) and all related components including water pump and tensioner replaced. I did oil change (Mobile 1 5w20 synthetic) including flush - replaced spark plugs and plug wires (note: used the bosch ultima plugs on last tune up- reduced performance- reduced gas milage considerably- gone back to standard NGK platinum plugs). tap noise is eliminated- engine is running smooth- far better performance and fuel economy noticed in first 500 miles. Before, I averaged about 360 miles per full tank- now I am getting about 420 miles per full tank of fuel. Note: good timing belt replacement information and possible tapping noise in valve train solution found at http://forum.planetisuzoo.com/viewtopic.php?t=13189