I have a 1999 RX 300 with 40,000 miles on it that has recently develop a gravelly knocking sound when I step on the gas going up hills.

I have been using 87 octane gas up till now with no problem. 93 octane gas seems to relieve the problem so I believe it is engin knock.

What fixes work for this car?


Thanks

 

I'm no gas expert, but most of the upper octance fuels contain detergents. Did one use of 93 clean anything from your internals? Doubtful. Did it help the acceleration and smoothness? Probably.

The 87 you've been using may have just been dirtier, and deposits may be robbing you of power; at least, that's sounds it sounds like based on your description of loosing power while applying throttle while traveling up hill.

I dunno for sure; I could be talking outta my butt, buyt that's what it sounds like from a conventional knowledge point of view.

Try using a couple bottles of fuel system cleaner over a few tanks, and see if this improves your throttle response and power.

Another angle: When was your last service? 30k? Can you tell from your nvoice if they chnaged anything that should have increased power like changing the air filter, new plugs, cleaned throttle body? If so, take it to teh dealer and say 'you did this, and I am losing power....'

 

plugsarent changed at 30,000

 

Unfortunately, your engine ECU coupled with all those knock sensors, should prevent you from experiencing ANY knock, much less audible pre-ignition. This has been a symptom sometimes associated with sludging, about which much has been written and involving great wails of despair, gnashing of teeth, rending of garments and on like that.

I'd suggest a trip to the dealer for sludge inspection. Your RX motor has an 8 year (from date of original purchase), unlimitied mileage warranty against sludge. Engine will either be repaired or replaced and any transportation expenses in the interim are covered (eg, a loaner).

Don't screw around with higher octane gas or injector cleaners. Neither should be necessary, period.