1998 Ford Crown Victoria LX 4.6L Use 89 Octane BP, Shell, Chevron gas. When the engine is under stress(acceleration or going up incline) the engine sounds like the valves are chattering. I can increase the rpm's and the chattering goes away. Had the same problem with 95 Thunderbird 4.6 and have heard other ford cars going down the road with this problem. Air leak? Don't really want to use higher octane due to gas prices and possible engine damage. Also, in the thunderbird, i used a bottle of octane boost and the next day a valve spring broke. Was the octane boost a possible cause?
it is not valve chatter, it is called Pinging, it is a fairly common problem, what it is caused by is hot spots in the engine, or by overly advanced spark timing, i would check your base timing, perhaps even back it off a degree or two, i would also run a bottle of marvel mystery oil, or gm top engine cleaner through a vacuum line to burn out the crud that has built up, the sum total of these repairs: about 15 bucks, the savings: your engine! as for your t-bird, it was the pinging that broke the valve spring, not the tank of hi octane. hope this helps
