need alittle help
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need alittle help
hey guys, i have a 1986 f-150 302(FI). Recently the truck started smoking black and running rough. The oxy sensor has been unplugged since i bought the truck about 7 years ago. The map sensor is new, throttle position sensor is new, dist cap and rotor are new, ignition module is new, ignition coil is new, fuel pressure regulator is new, wires, plugs, ect. are new. i got the codes and it gave me 21, 24, 31. I really dont know much about ford computers so any help would be great. The truck will rev up fine but when idiling it floods the plugs. i had someone tell me that it could be the EEC computer, but i really dont wanna change that unless i have to. thanks CT
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From: Quad Cities, IA
The O2 sensor is *unplugged*?!?
That's the first place to start. Your computer-driven fuel injection system NEEDS a reading from that sensor in order to tell the injectors how much fuel to dump into an engine. If it's getting a zero reading, it's thinking "Oh, I'm not giving the engine enough gas! Let's just dump more in there..."
If the O2 sensor is bad, replace it. If it's good, plug it back in. That's pretty much the first thing you need to do before looking into other issues.
That's the first place to start. Your computer-driven fuel injection system NEEDS a reading from that sensor in order to tell the injectors how much fuel to dump into an engine. If it's getting a zero reading, it's thinking "Oh, I'm not giving the engine enough gas! Let's just dump more in there..."
If the O2 sensor is bad, replace it. If it's good, plug it back in. That's pretty much the first thing you need to do before looking into other issues.
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Changed o2 sensor, just as i suspected it did nothing. The truck is flooding while starting, even if i hold pedal to the floor it will not clear the cylinder. I have to pull plugs and physically dry them to get the truck to start. Once i pull plugs and dry them, the truck starts right up. What determines fuel mixture while starting? also i tested fuel pressure, and vacuum pressure both are good.
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From: Quad Cities, IA
Hmm... This one is a bit out of my scope of knowledge. Seems like there must be a "fast idle" setup in there that is WAY out of adjustment, and is dumping so much fuel in there that it's flooding out your engine.
On a carb'd vehicle, you can adjust that easily... On an EFI setup, that's a bit trickier. Perhaps there's a sensor that's involved here that monitors cold idle fuel mixture? Air temp sensor perhaps?
Hopefully someone will be along shortly with some more information on this subject. Frankly I'm quite curious on this issue myself, now that you brought it up.
On a carb'd vehicle, you can adjust that easily... On an EFI setup, that's a bit trickier. Perhaps there's a sensor that's involved here that monitors cold idle fuel mixture? Air temp sensor perhaps?
Hopefully someone will be along shortly with some more information on this subject. Frankly I'm quite curious on this issue myself, now that you brought it up.
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From: Virginia
21 is the engine coolant temperature is out of range. If the computer thinks the engine is cold, it will throw more fuel to it.
24 is the air charge temp sensor is out of range. Same as above.
31 is something in the emissions circuit is out of range.
That is a lot of sensors going bad at once. I think I would look the wiring over and see if these have something in common. You may have a bad wire in the engine harness.
I found all this out by going to www.fordfuelinjection.com
24 is the air charge temp sensor is out of range. Same as above.
31 is something in the emissions circuit is out of range.
That is a lot of sensors going bad at once. I think I would look the wiring over and see if these have something in common. You may have a bad wire in the engine harness.
I found all this out by going to www.fordfuelinjection.com
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Likely sounds like a wiring issue or possibly computer. I've worked on cars that one of the injector drivers in computer was bad and pretty much telling one injector to spray fuel all the time causing a VERY rich condition.
Also,like someone else said. If your Coolant temp sensor and/or Air temp sensor are open or wiring damaged to them, the computer thinks they are reading around -40 or so which would require more fuel because colder air is more dense. You might be better off in the long run to pay a reputiable tech to diagnose it for you rather than throw parts on it unsure if they will fix or not. IF you know how to use a multimeter and have a manual, you should be able to check the resistance of the coolant and air temp sensors and confirm if they are good or bad. Good luck! keith
Also,like someone else said. If your Coolant temp sensor and/or Air temp sensor are open or wiring damaged to them, the computer thinks they are reading around -40 or so which would require more fuel because colder air is more dense. You might be better off in the long run to pay a reputiable tech to diagnose it for you rather than throw parts on it unsure if they will fix or not. IF you know how to use a multimeter and have a manual, you should be able to check the resistance of the coolant and air temp sensors and confirm if they are good or bad. Good luck! keith
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From: Virginia
I may have made a mistake. I forgot to say you may get a code 21 if you pull the codes, and the engine is below 50 degrees f. This is also true for the code 24. So if you pulled the codes with the engine cold, and it's cold outside, you will get the codes.
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