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Runs great at sea level. Above 3000'alt. idles fine, in neutral revs fine, in drive under load cough's, chugs and pops through the air intake intermitantly. If I let it sit for an hour or two, runs good again until it wants to give me a headache again. 93' 460 in a 34' bounder with fuel injection. New air filter. I guess my question is, is there a computer or something that compensates the air/fuel mixture at altitude? I am almost positive this is a fuel/air problem and not ignition or heat related. Anyone with information, it would be greatly appreciated.
Greg
You didn't say what year this is. I know that early production Ford fuel injection only reads the altitude when the engine is starting. It then uses this value untill the engine is shut off. Shutting them off for a few minutes cured the problem untill the next big change in altitude. I don't know if this is your problem but thats my 2 cents Good Luck
It's a 93. Forgot to mention new fuel filter and have good supply of fuel. When it's acting up, shuting it down does not help except letting it sit an hour or so.
Thanks for your input,
greg
Your story sounds quite familier. At the same time you were having your problem I was coming from St. Paul, MN heading to Reno, NV and was having very similiar troubles. It turned out to be Ethenol vaporlock. The cure is to not buy any fuel with over an 87 octane rating. It seems to be popular now to blend ethenol into fuel to immitate higher octane and without labeling the pumps as such. The problem of vaporlock is enhanced with elevation. Additionally I added.1(one tenth) of a gallon of diesel per tankful. Theory is it either changes the viscosity of the fuel or coates the inside of the tank, lines and injectors to stop the ethonel from dissolving the rust that is inherently in the tank and lines, or both. Feel free to contact me if you desire further clarification. Lots of luck.