Hello All,

Hoping for some opinions on my next step. I've got a 99 Epxy with the 5.4 and towing package. I tow a 4100lb travel trailer at times and have been having a bad spark knock when under load. Sometimes even going downhill slightly with the trailer. I also can get the Epxy to do it without the trailer at times on a steep grade before it shifts. I do not tow in overdrive and I use 87 octane. I usually tow around 60-65 on the highway without any trouble from the trailer. This is what I've done so far:

First Ford dealer test and said everything was in factory limits. They did clean the Mass Air Sensor. They said that my trailer is close to being too-much for the Expy (they said it with a straight face!). They could also get the spark knock but said thats the way the factory has it set.

Second non-Ford shop shop checked my plugs and EGR valve. Both were good. They did this without appt and after hours so they were not able to do much else.

Third shop who was recommended by the second, a Lincoln-Mercury Dealer, laughed at what the first dealer said. They reset the computer and reset the octane to 87. He said the timing should be retarded about 3 degrees. They also suggested trying a GM carbon cleaner as the Ford cleaner doesn't do much. Have not done the cleaner yet.

After this, I towed the trailer this past weekend and still spark knocks. Not as bad, but at 60mph on the flat highway, it still had some knock. I switched to 89 octane on the way home and that helped some.

Any ideas of what to do? I've spoke to several other Expy owners towing heavier trailers with 4.6 and 3.55 gears and they have no problems. Help?

Todd

 

I have a 99 with a 4.6 and can tow that much with no trouble. A 5.4 should tow a lot more. At around 75k my plug wires started going bad, and two of the plugs, so I replaced them all. Runs much better. I don't know how many miles you have, but you might try the wires. Good luck.

 

I guess I should have gave that info also - I've got about 73k miles on it.

 

Did they check the knock sensor? I had one go bad on a Town Car once, replacing cured the problem.