I recently purchased a used 94 F150 inline 6. I'm not too intuitive with automotive issues. I recently drove across the country in the truck. I did change the oil prior to the trip with synthetic 10w30. The engine itself is a rebuilt engine with supposedly less than 10,000 miles on it. The engine certainly appears clean and well maintained. The truck has about 240,000 miles on it. The truck gets horrible gas mileage. So on my trip I was happy to use 85 fuel instead of 87 since it's cheaper. I'd never seen 85 and had no idea it existed. I didn't know that it was much more horrible than 87 either. The trip itself was about 3300 miles. Around 2700 miles engine knock started to make the noise. Since I was close to home, I continued driving. The knock is now severely worse. Truck still starts, but I don't want to drive it any longer to avoid even more damage.

My question is, is there anything I can do myself to fix this knock without having to bring it in to a shop? Will using fuel cleaner work? Is it even worth it?

Any help is appreciated.

 

back the ignition timing off 2 degrees. You'll need a timing light to do this or just use better fuel...

Or lower your T-Stat temp... the hotter the t_stat you use the higher the octane requirement

I use a 160 t-stat and can get away with 85 octane fuel

 

sounds like you are hearing pre-ignition, aka knock.

85 octane is used in higher altitudes. back at sea level its not good. and as engines age, some need higher octane to run properly. with your fresh rebuild this should not be the issue.

if you have half a tank, top it off with premium, and the mix should bring the octane rating up to 89 and be safe. If you have a full tank, find a way to empty it and fill it with 87.

octane booster in a bottle does almost nothing, dont waste your money.

 

One thing I think we should do here is determine what kind of knock you have. A detonation or knock and ping from poor fuel is more prominent on acceleration and under load. It should pretty much go away during idle and cruise. You should hear it up near the heads and exhaust manifolds. It kinda sounds like a tractor or a diesel motor. If that's the case some good fuel and a tune should be fine. My concern is not knowing who rebuilt the engine or how you may have a rod knock. If you have a constant knocking noise from the bottom of the motor that is steady in time with engine speed you may have a more serious problem.

 

Thank you for the help, and insight. Unfortunately, the only reason I had any knock was because of my own dumb dumbness.

I checked my oil level on un-level ground, so it looked like it was full. However after changing my oil, I really only had 1 quart of oil in the motor. I put a new oil filter, and new oil........ Now the knock is gone.

I have however done it again. I forgot to coat the oil filter with oil before I put it on. I'm not sure what this will do, now that I've already filled it up with 6 quarts.

 

Yeah that will do it. Filling the filter keeps the pump lubed at startup after the oil change and gives you a more accurate reading when filling. Coating the gasket and threads keeps the filter from sticking and helps prevent leaks. I would loosen the filter a little until the oil spills out and coats everything so it doesn't stick. But there should be no harm done.

 

coating the gasket ONLY serves so the rubber doesnt bond to the metal block. try taking one off after a year or so that hasnt been lubed...comes off in chunks