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- 1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks (https://www.ford-trucks.com/forums/forum37/)

- - oxygen sensor (https://www.ford-trucks.com/forums/34435-oxygen-sensor.html)

hey everyone i've got an 85 f-150 with the 302 efi. When i bought the truck it had headers with no oxygen sensors. the truck ran great until recently, now once it is warmed up it acts up, when you are driving it bucks and acts like it is missing and when it is sitting idling you can smell unburned gas in the exhaust. i have replaced cap, rotor, wires, coils, ignition module, pick-up (in dist.), fuel pressure regulator. does anyone have any ideas to what would cause this. one other thing, does anyone know of a way to have the o2 sensor run in open loop at all times. thanks

[updated:LAST EDITED ON 05-Feb-02 AT 01:34 AM (EST)] I am having the same problem and have been looking for a solution for the past week. My truck (F-150 4x4 302 EFI) starts spitting and sputtering as soon as I crank her up, and acts like she wants to cut off, but she doesn't, just sounds like skipping but it isn't. However, when I get her wide open she will fly, and run smoothly.
I have manifolds and a fairly new oxygen sensor, so I do not think that the o2 senor is our problem. I will tell you that I have replaced the throttle control sensor on the throttle body, the distrubutor cap and rotor, and wires. Fuel regulator sensor, and feul filter.
I really think that our problems are a combination of things with the trucks computer. Here are some good segestions that I am looking into replacing. What ford calls the TFI module on the side of the distributor, which you might have replaced. The timing advance sensor, and who knows what next. A good place to start is your throttle body, check all of the sensors and air bypass valves, to make sure they are clean.
The funny thing is that it does not seem to be skipping in one cylinder, and there is those fumes of unburned gas, maybe there is a bad mixture. I thought at first that it was bad gas, but it wasn't. Then I thought that my vaccum hoses were lose, but they are fine. So, who knows, If you find out, please let me know, because this is something unusual.

-- adamham76

I talked to one of my friends and he said that your truck will run fine with out an oxygen sensor, that would not make the truck run as rough as it is, I am assuming that there is not smog pump on your truck also. Let me know when you find out what was wrong.

Thanks,

the other night i was messing around with the truck, and i had it sitting, idling and it shut off, at first i thought it was out of gas so i put some gas in it, turned the key on and off a few times to pressurize the lines and it still would not start. the next day i decided to pull a spark plug out and test to see if i was getting any spark, i'm not. all ignition components are new. any other ideas?
thanks