'86 Bronco 5.0 problem, please help
'86 Bronco 5.0 problem, please help
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Senior User
Joined: Dec 2000
Posts: 111
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'86 Bronco 5.0 problem, please help
I have an '86 Bronco 5.0 EFI that is running like it has a stuck valve but after pulling the valve covers, that's not what i see happening so now i'm stumped. Symptoms are: Won't start without my foot in the gas a little. Doesn't idle. Once running, puffing blue/white smoke out the drivers side exhaust pipe along with alot of gas, black smoke out the pass. side. (I have headers & true dual exhast) Running very rough. Useing an extreme amout of gas. Gas in Oil.
I changed plugs, wires, cap, rotor, EGR valve.
Could this be a fuel injector plugged? I'm not sure if one plugs do the others pump more, hense the gas in oil/exhaust.
Something to do with fuel pressure?
I'd appreciate any input here. Really miss my truck, been down all week, now that the weekends here and i have the time i'd like to get it going. Thanks Alot.
I changed plugs, wires, cap, rotor, EGR valve.
Could this be a fuel injector plugged? I'm not sure if one plugs do the others pump more, hense the gas in oil/exhaust.
Something to do with fuel pressure?
I'd appreciate any input here. Really miss my truck, been down all week, now that the weekends here and i have the time i'd like to get it going. Thanks Alot.
Post Fiend
Joined: Nov 2002
Posts: 9,987
Likes: 7
From: Memphis, TN
'86 Bronco 5.0 problem, please help
Where's your oxygen sensor (HEGO)? Even on a dual exhaust, there should be a crossover tube on any EFI with the HEGO in the middle where it can read both streams.
It sounds like you have a LOT of extra gas going into the engine, so pull the vacuum line off the fuel pressure regulator (FPR) and see if it's leaking gas into the intake. FPRs are known to do that, but they're not expensive.
If there's no gas in the vacuum line, pull the codes and put a gauge on the fuel rail to see how much pressure you have.
It sounds like you have a LOT of extra gas going into the engine, so pull the vacuum line off the fuel pressure regulator (FPR) and see if it's leaking gas into the intake. FPRs are known to do that, but they're not expensive.
If there's no gas in the vacuum line, pull the codes and put a gauge on the fuel rail to see how much pressure you have.
Post Fiend
Joined: Nov 2002
Posts: 9,987
Likes: 7
From: Memphis, TN
'86 Bronco 5.0 problem, please help
Your computer has been learning how to cope with the extra gas, so you'll have to make it forget by unhooking the battery for ~5min and then let it relearn by driving for ~10mi. It may run slightly rough while it's learning, but it should clear up fast.
Senior User
Joined: Apr 2002
Posts: 279
Likes: 1
'86 Bronco 5.0 problem, please help
On my '86 302, with a single exhaust, the O2 sensor is located on the passenger side exhaust manifold.
So, on the stock system the O2 sensor does not receive input from the drivers side exhaust.
So, on the stock system the O2 sensor does not receive input from the drivers side exhaust.
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Fleet Mechanic
Joined: Aug 2001
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From: Round Rock, TX
'86 Bronco 5.0 problem, please help
Weird; I seem to remember that on my '86 EFI Bronco it was on the crossover where it is nowadays... But memory may fail me.
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Senior User
Joined: Apr 2002
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'86 Bronco 5.0 problem, please help
Maybe there was more than one method?
On mine the two sides combine together by entering a dual in-single out cat.
There is no place to put one prior to the cat that gets both sides.
At least not without going to a dual O2 sensor setup.
On mine the two sides combine together by entering a dual in-single out cat.
There is no place to put one prior to the cat that gets both sides.
At least not without going to a dual O2 sensor setup.