Cackeling Noise Or Simialer Under Acceleration

[Maverick73]

I don't know if cackeling is the best description of ths noise. I believe this noise starts at about 40 MPH under hard acceleration goes away after maybe 70 MPH does this mainly from a stop or slow speed. Any ideas on what this could be? this is a 1999 Explorer XLT, 5.0L V8 2WD 82,000 Miles.

Thanks

 

[Turdle]

Does the noise seem to be coming from the passenger side of the engine?

Exhaust leak?

 

[Cobraguy]

Is it pinging??? (detonation)

 

[Maverick73]

Is it pinging??? (detonation)

After further research I believe it's "spark knock" I guess the first thing to do is use higher octane gas, I'm currently running 87 octane fuel. If that doesn't fix it I guess I'll have to take it to the mechanic.

 

[Cobraguy]

I have to tell you...the 1999 5.0 in good tune should run fine on regular...and is recommended in the owner's manual. We have to run the same swill California does and I never get detonation on 87 octane. But I have a fresh engine too. Maybe you have some carbon build up in the cylinders or on the valves contributing to your problem. You might try to use Sea Foam or a similar procedure and see if that helps.

 

[ThePhoenix]

bad spark plug wire will d o this if its arching out

 

[Maverick73]

Update: I put it some 89 octane fuel. It seems to have corrected the noise either all the way or mostly. I don't know if from now on I should get 89 octane, or take it to the mechanic and have them clean it and go back and try 87 octane? Opinions are appreciated.