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1986 F150 5.0 bucking

 
Old 01-07-2019, 09:27 PM
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Default 1986 F150 5.0 bucking

Hello all. I have a 1986 F150 5.0 multiport FI that I saved from a junk yard. It doesn't have O2 sensors on it. There is custom duel exhaust with no converters on it. Does anyone know if this truck is supposed to have them and how many? I can't find any wiring anywhere that would suggest that it even had any on it to begin with. Also it has a funky thing it does. When started it will not take the throttle. If I push too hard it will buck and jump. If I push lightly it will slowly accelerate until it reaches a certain rpm at which point it will buck and jump again. If I shut it off and restart it runs perfect for about 2 minutes then starts that jumping again. Sometimes it doesn't do it at all and runs great. I have replaced a bunch of stuff trying to fix it to no avail. I have replaced distributor, ignition module, map sensor, air charge temp sensor, computer, timing chain and gears, TPS. Deleted egr. Help please!!
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Old 01-07-2019, 09:40 PM
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Fuel pump and or filter, inline fuel filter is a cheap shot
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Old 01-07-2019, 09:47 PM
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I forgot to say fuel pump was replaced. Fuel filter has been replaced as well. The tank was clean when pulled to replace fuel pump. Has good fuel pressure.
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Old 01-09-2019, 09:25 PM
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I'm curious how it's fuel injected without O2 sensors. That part makes me wonder if somebody sent it to the wrecking yard before finishing the header install. Can you see any dangling wires that an O2 sensor could plug into? Have you crawled under it to see if the O2 senors are underneath in a place not easy to spot?
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Old 01-09-2019, 09:49 PM
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Yes I have look all over for them. It has stock manifolds on it. It did have some exhaust on it when I got it but no O2 sensors or wires anywhere. I'm wondering if the bucking and jumping is wh they sent it to the yard. How hard would it be to convert to carberated?
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Old 01-10-2019, 12:06 AM
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Originally Posted by Turbo4man View Post
Yes I have look all over for them. It has stock manifolds on it. It did have some exhaust on it when I got it but no O2 sensors or wires anywhere. I'm wondering if the bucking and jumping is wh they sent it to the yard. How hard would it be to convert to carberated?
Well, I wouldn't convert to a carb unless you have a very substantial amount of components missing. You would have to strip your entire computer and emissions system and switch to a vacuum advance or high dollar after market distributor and ignition control unit. Also, there may be passages in the intake and heads made for the Exhaust Gas Recovery system which will end up plugged with crud, so you would probably wnat an aftermarket intake. It might help to check your vin numbers and find out exactly which model you have, mainly look for whether or not it was made to be sold in California. Most vehicles had standard smog systems with the exception of the smog pump itself, some do not come with those, California models went the extra mile and had it all. I'm not typically a Ford guy, so I'm sure someone else hear can tell you what different types of Fuel injection and or smog configurations there were for your year if any. If Ford is like Dodge, then they had several different models even among the same class. For instance Dodge made standard duty 3/4 tons, and Heavy duty 3/4 tons. Heavy duty were equipped with the larger front axle, more rear springs, and a smog pump and related equipment to cope with the extra fuel burned by towing and work duty. .The standard 3/4 ton did not come with a smog pump, then there was the California model which had everything. Ford may hove done similar things. I think you will definitely have to crack open a Ford repair manual and start studying everything about the ignition system, fuel injection, and emissions control. Read carefully too. You should definitely check your vacuum hose routes too, to make sure it's all hooked up right. I would just start by looking for missing components. It really sucks when you have a vehicle that's been tampered with.
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Old 01-12-2019, 08:55 PM
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The wire for the O2 comes from the computer harness on the drivers side, across the back of the engine to the passenger side near the back of the exhaust manifold.
Careful, some vacuum lines from the passenger fender run parrallel behind the engine to the drivers side vacuum tree, etc..

Last edited by vjsimone; 01-12-2019 at 08:58 PM.
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