;94 F150; 4.9L; automatic.... bought a Ford 2000 tractor and have hauled it on a U-Haul car carrier pulled behind my F150.. For the most part all goes well. However, on long hauls uphill I'm getting some valve chatter with the engine under load. No problems on slight inclines or level ground or downhill. Slight increase in engine temperature also. Is there anything that I can do to overcome the valves chattering other than upgrading to a 250 with a v8?

 

Sounds like detonation to me. Have you tried using a higher octane gas to see if it stops?

 

No, been using regular 87 octane. Gotta go pick up my tractor next week and will fill up with a higher octane and see what happens. Thanks.

 

Check for codes first.

After checking for codes, I'd start off with checking spark plugs, timing, EGR valve and vacuum hoses. Spark plugs should be Motorcraft or Autolite plain copper core, your EGR valve could be bad or outright the wrong part (if previously replaced). Leaky vacuum hoses could cause issues as well.

 

Picked up my tractor last week and, on the way, gassed up with high test to see if that would solve the valve 'rattling' problem. It did. So, would that indicate that my timing might be out? I don't believe I have to start using high test all the time. Normally, I use 87 octane regular and occasionally run a can of SeaFoam when I fill up. I will run the codes and see what comes up this weekend.

 

There's a few different things that coould be causing it with the lower octane. The timing could be off. Plugs could be wearing out and causing a hotter spark. The engine could be running hot and the gauge could be wrong. If you get gas at the same place all the time it could be some bad gas. There could be carbon buildup on the pistons. The carbon buildup causes a rise in compression.

 

The plugs are easy enough to change and are probably due and a can or so of SeaFoam might help the carbon. I do run a can thru it occasionally. I might drag out my timing light this weekend and take a peek to see what lines up. Thanks for your insight.

 

Also, check the fuel pressure and replace the fuel filter. If the fuel system isn't supplying enough fuel under load it will cause it to run lean and cause detonation.

Just remember that the clattering you hear when detonation occurs is the piston itself slapping around inside the cylinder. So even if you have to run a higher octane it's cheaper than having to rebuild the engine.