My 1987 Class C motorhome on an E-350 chassis with a 460 has developed a problem I cannot identify, but it seems like a timing problem to me. I usually set the cruise control at about 65mph and it runs along quite well, but the last trip I would occasionally get a small backfire, that I could hear, but not feel, just a little "pop". Also, once when passing a line of semi trucks, I kicked it up to about 72mph to get around them and all of a sudden it just starting slowing down. The motor sounded smooth, just no power. I was about to jump in my Ranger I was towing and PUSH the motorhome! It dropped down to about 55, and I fell in behind the truck to let other traffic pass, and it would then accelerate and I passed the truck at about 75 or better after that. Power on the hills has dropped too, but it seems ok sometimes. I first thought it was a fuel problem, but I changed the filter and checked flow out of the fuel line and it looks good. The timing at an idle is fine, the mechanical advance seems to be working, but doesn't the Dura-spark module control timing too? Of all the Fords I've owned, the only problem I've had with a Dura-spark was no spark at all not an intermittant problem like this.
Any help would be appreciated.
90 Ranger 4X4
91 Explorer 4X4
94 F-150 4X4
87 Ford Moho (ailing)
Ken, have you tuned the engine up lately? It could possibly be a cracked ignition wire or boot right where the wires go to the plugs. The heat from the exhaust manifold could have dried the wires out. Also check coil. Make sure that there are no cracks in it and that it is sending a blue spark to the plugs. I have had similar problems with wires on my 92' f-250 (351 engine). I have seen the coil act up like this on all of my f-700's at one point or another. 84', 86' 87' & 89'.370 engine. Also check wiring to distributer for chaffing on engine block. Good luck.... Jakegypsum // Ford fleet, soup to nuts.
When the wind is right, you can hear those Chevy's rust..........just listen.
I had a vacuum leak going to my vacuum advanced that caused a very simular problem....Ran great...would back fire...lost power and slows down. I would take my foot off the gas and then would run fine for a while.
Just A note on fuel filters for the 460 cab & chassis models, some models had 2 fuel filters per vehicle. One was the 3 line filter between the fuel pump and carb, and, some had a canister filter between the tank and fuel pump....check very closely for the "extra" filter. Also, the vacuum line tip is a good one....seen that one many times as well.
Yes Philip, you're right. Ford quit using that canister filter around 1992 or so because of the problems it was causing. No one knew about it to change it. I was told by a Ford dealer to remove the canister filter and just run the inline filter.
[font size="1" color="#FF0000"]LAST EDITED ON 31-Dec-00 AT 10:03 PM (EST)[/font][p]Hi Ken
Can you tell me if your truck is EFI or Carb? If it is EFI, do you have a MAP sensor or MAF sensor? I've been looking for a conversion kit for my truck to MAF. 96 F-250 460/E4OD. I've been told that a few Motorhome Chassis had MAF up till 1994 or so.
Have you ever heard of a MAF conversion kit for the 460?