ive got a 97 150 with a 4.6 auto trans 4x4 its been sparkk knocking a while now and im not sure how to correct. i thought it was just the cats going bad cause it struggles to pull hills but now im fairly certain its a spark knock i have changed the plugs wires tps and the iac. =my check engine is not on i have a few ideas but before i just throw parts at it does anyone have a idea what could be causeing this. also i buy my gas at the same hess station every time im also running 87 octane and the truck is fairly stock it has cold air intake and a 1 in 2 out muffler thats it odometer reads 238000 not sure how accurate though
thanks for the help

 

Your not supposed to run anyting under 89 in these. 87 octane is to low for the modular 4.6

 

I've only ever run 87 octane in my 99 4.6 and I've never had any issues