i recently just got a 1985 f150, it has a fuel injected 302. However it is not running right, it will start up and idle kind of fine (around 1100rpm) but is not very responsive at all off idle and will intermittently backfire and misfire through the intake.. i have talked to several mechanics and they all told me it was due to bad fuel as the truck was sitting for about 5 years.. but we drained the fuel added new gas and it does the exact same thing... me and my dad can not figure it out.. so any help would be great..
When you drained and changed the gas did you change the fuel filter? And did you use a good fuel treatment like the Lucas product? Get an OBD 1 code reader and see what the computer may be storing. Also, if you haven't driven it for any distance, check your alternator belt tension, battery connections, and that your voltage regulator is putting out enough power. The truck will run exactly as you described if the battery has just enough power to start, but the system isn't charging.
I had similar trouble after swapping a '90 engine into my '85. It all went away after I unplugged the knock sensor. It's in the lower intake, driver's side, right about the middle. It resembles an AC Pressure switch, kinda.
Also- have you replaced the plugs? I had a new set in the engine I took out, they fouled after ZERO miles. All the farting around in the driveway did them in.
5 Years? Tank is probably rusted to hell. Take the fuel filter out and see what's in it. If there's rust-dust youll need to drop the tank and clean it out.
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