cgert

Is threre a Knock or ping sensor on the 5.7L engine, and where is it located? Mine pings even with 89 octane fuel.

MT-2500

Get a scanner on it and see if the knock sensor and egr valve is working right.
The knock sensors are on sometimes in front of starter.
Check wiring real good for knock sensor problems.
If egr valve is not opening you will get a engine knock to.
Get it scanned and post back codes.
MT-2500

bearsfan_54

Are you getting a check engine light? If so, what is the code? If not, your still going to get valve knock whether you use 87 or 89 octane fuel. Try running your tank down to around a quarter (never run below that because the fuel pump may overheat as it is inside the tank). Top her off with a 93 octane (preferably BP Amoco Ultimate or Shell's 93 octane) fuel and see what happens after about 50 miles or so.

If you need to change out the knock sensor. Be sure to let the engine cool completely before performing this task as coolant will pour out like a siv. The knock sensor on your engine is located directly in front of the starter at the rear of the engine block. It's about 38 bucks at the parts store. Make sure the threads on the sensor have anti-seize coupound on them before bolting it in the block. Most sensors should come with the compound already on the threads.