I have a 97 F150 4.6L V8. Runs like a charm with the exception of a spark knock when under acceleration or load. When i put higher octane gas in, it helps the problem significantly. Any ideas on the cause or solution to this problem? Thanks.

 

I would recommend inspecting the plugs to make sure they are still good and double check they are seated properly. Make sure your cables are also not frayed and that they are attached properly. Good luck.

 

SPARK KNOCK

Definition: This is the pinging or rattling noise sometimes heard during acceleration that indicates detonation is occurring inside the engine (See Detonation). Related Terms
• Detonation






Spark knock can be caused by a variety of things including using low octane fuel, over-advanced ignition timing, too much compression (often due to a buildup of carbon in the combustion chamber), by an inoperative EGR valve, and/or by too much heat. If switching to a higher octane fuel doesn't cure the problem, the cause should be investigated because prolonged or heavy knocking can damage the engine.

 

Thanks....Just curious...has anyone else experience this problem with their 97?

 

Yeah, I have a 97 4.6 that used to have a fair amount of spark knock. About a year ago I cleaned the maf and temp sensors, the throttle body and the air ports around it and ran seafoam through the brake booster line and the gas tank. All that made it much better, it was then pretty much limited to high rpm. After searching the threads here it sounds like it's a never ending battle with the 4.6.

 

As a tech point, do not use ping or spark knock interchangeably with detonation.
They are not the same thing although related.
Detonation is "uncontrolled" ignition by other than the spark plugs.
Ping or more properly 'spark knock' is ignition by the plugs at too early a time in the compression cycle, for the fuel being used.
The lower octanes are faster combusting once ignited and is why the higher octanes' slower combusting, helps with the problem.