Hey, I'm new to this. I've got a 97 f-150 supercab with a 4.6. The truck runs great except for when pulling a trailer. It starts to "labor knock" when you accelerate. I use 87 octane. Could the truck have bad gas or just a worn out engine? I have 138,000 miles on the truck and they aren't tough miles. The total load is around 5500 lbs. on the trailer. I haven't used this truck to pull loads before now. Thanks for any help.

 

You’re working the truck harder and running hotter when you’ve got something in tow and now you’re experiencing pre-detonation. The quick and easy solution is to move up a grade of gasoline when you tow. The higher octane raises the flashpoint to help alleviate the pinging.

If you want a long-term solution, you’re going to have to first determine the actual cause for pre-detonation other than it’s just “working harder now.” I’m really not the right person to help with that. Does anyone know some common causes for knocking and pinging?

 

Check the Engines forum for the pinging issue. I know there is/was a lot of disscussion on the 4.6 pinging. Seems to have to do with the computer program.

Try resetting yours and see what happens first (it's free!). Just disconnect the negative battery cable, turn on the lights (yes, I know they won't come on, it just helps drain any residual power from the system). Let it sit for at least 15 minutes, turn lights OFF, reconnect battery, start truck. **VERY IMPORTANT** Do not touch the gas pedal during this initial startup. The computer needs to find it's own idle setting. Let idle all by itself for a couple of minutes, then go drive around as you normally would. Let it get up to full operating temp and if you can hit the highway, that'll be good too.

Might not resolve the issue, because there could be a million other possible causes too. Carbon in the intake, clogged fuel injectors and on and on.

The engine section should help more too.

Good luck!

 

My '88 F-150, 302, 5-speed will sometimes knock like that, but only when I'm in too high of a gear when pulling a heavy load. Example, pulling 3,000 pounds up a hill in fifth gear. Not good. Downshift to fourth were it should be and it flies up the hill and sounds good doing it. 188,000 miles and isn't slowing down.

 

run some fuel power through your engine and clean up the oil with some lube control, works for me every time.