i know this has been covered before but i can't seem to find any related treads. 1996 F150 5.0 auto 4x4 XLT SC short bed. with 269K miles on the truck. eng and trans have around 160K now. i put the last 70K on them. when i installed the eng. i replaced the timing chain / water pump / oil pump / cleaned everything on the intake and replaced all the intake gaskets / new plugs wires / cap / rotor bug / coil / radio suppressor ( used ). since the install i have replaced the following radiator / antifreeze / fan clutch / fuel filter / ignition module / rear fuel pump / and 4 new 31x10.50x15 tires. in short i have rebuilt or replaced most everything on this truck. i drive it about 80 miles a day. over the last couple weeks it will intermittently get spark knock. sometimes ever so slightly and sometimes very bad no matter what tank it is on. both tanks are good. i have checked the timing with a gun and pulled the spout. it's @ 10* BTDC. the balancer rubber looks good so i am convinced it did not slip. i checked the plugs and they look good. the wires are routed properly and have the proper clips on them. no eng light and no codes stored. no vacuum issues or leaks that i can find. the only thing i have noticed is oil residue on the bottom of the air tube at the Y going to the throttle. will be installing a new PCV and fuel filter this weekend. the truck runs fine other than the ping. has decent power and is pulling around 16 MPG with mixed driving. as i stated i replaced the ignition module with a new one from autozone about 4 months ago. ( old one went out suddenly ) it was all i could find at the time. could this be responsible for the spark knock? if not what else could cause the problem?

 

First, if you are experiencing bad knock, run 93 until you figure out your issue.

Pull codes, and check fuel pressure *under load*. When is the last time the fuel filter was changed?

Check the intake/pcv hose for excessive oil, as oil causes ping.

Have you ever tested the injectors? A lean cylinder can be tricky to diagnose, often times requiring removal of injectors to test and confirm their operation. Pulling and reading spark plugs is another way to look for a lean cylinder.

 

i will be replacing the fuel filter and pcv this weekend. both where last changed about 60K miles ago. kind of got away from me. will check the pcv hose when i change the pcv. there is no codes stored so whatever is causing it to ping is not setting a code. i will look into the injector's. thanks