I have a 98 F-150 4.6 Auto, 3.55 gears & 2-wheel drive. I bought it with 21,000 miles on it and never noticed it pinging when I first bought it, and for the first two years that I owned it. It does ping now under hard acceleration, especially uphill. If I use 91 octane it helps. My questions are, what changed that it pings now, and is this something to be concerned with? What are some remedies?

PUMA

 

Possibly combustion chamber deposits, or it's time for new spark plugs, or you have a vacuum leak, or your EGR system is not working properly. How many miles on it now?

 

Sounds like it's time for a tune up. Run a can of Sea Foam through it, change the plugs and wires and all filters. This might help lessen the pinging.

 

It has 75,000 on it now, plugs were changed @ 60,000. I have never changed the egr, where is it? It has original wires. No check engine light, except for the other day when I pulled out and had to really get on it to get into traffic. That triggered a check engine light. I disconnected the battery for a few than reconnected it, it has not come back.

 

It may be a throttle body with carbon buildup. I have seen several post in regards to cleaning the throttle body and IAC and that pinging went away after cleaning.

 

My 1998 4.6l 4x4 , 3.55:1, has pinged since new when towing 2000 lb boat and trailer combo, always use 89 octane for towing

 

My 1998 Ford F150 4X4 has pinged since I bought it with 34000 miles. i have been running high octane for years, even when it was ridiculously expensive. I have heard of people saying something about a knock sensor but haven't investigated further.