efi 460 running extremely rich
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efi 460 running extremely rich
1997 ford f250hd 4x4, 460 efi motor. ever since we put headers on my truck and 3" true duals, it has been running very rich. the o2 sensor is placed in the driver side pipe and it is throwing a lean o2 sensor code, could this be why? can the o2 sensor richen the af mixture that much? it smokes at idle and smokes when i get into it, and fuel mileage is crap. like 6 mpg. smog pump is deleted, egr tube is closed off, intake tube horns are cut off,msd rotor cap with accel coil and 8mm wires
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Joined: May 2011
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No other codes? Where did you put the o2?
Check fuel pressure (and make sure the pressure regulator isn't bad, pushing fuel into the intake manifold), and check for leaks in the exhaust upstream of the o2.
If those check out, unplug the o2 sensor (forcing open loop) and see if it's the computer causing the rich condition. If it stays rich, you likely have a sticky injector that is staying open.
Check fuel pressure (and make sure the pressure regulator isn't bad, pushing fuel into the intake manifold), and check for leaks in the exhaust upstream of the o2.
If those check out, unplug the o2 sensor (forcing open loop) and see if it's the computer causing the rich condition. If it stays rich, you likely have a sticky injector that is staying open.
More Turbo
Joined: Feb 2015
Posts: 508
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From: NE Ohio
I had similar situation; running rich and throwing a lean code. When I red the plugs, one cylinder wasn't getting fuel (bad injector condition). The o2 picked up the fresh air and richend the mixture. I know its a long shot, but after you check for upstream leaks, maybe read the plugs. Like previous post said, could be one stuck open. Another way to tell is to put stethoscope on the injectors and listening for the tick.
Good luck,
-Glaser67
Good luck,
-Glaser67
Lead Driver
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It could bewhy for sure. Easy way to test for a stuck injector is to downshift and engine brake down a steep hill. Get the rpm up to 3000+ with no throttle on decel. With the rpm above idle, and 0 throttle, the computer commands 0 fuel from the injectors (In other words, they're "off"), and it should be smooth. If the engine is stumbling and fumbling on decel with 0 throttle, an injector is stuck.
New User
Joined: Mar 2017
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From: Loomis CA
My cousin has been through the same issue, he has a 96 460 mated to a zf5. We took the boat out to the lake for the morning, and when we returned it was idling so rough it sounded cammed. Backfiring if I eased up on the gas too quickly. A quick check on prodemand5 and we replaced the injectors, changed nothing. Replaced the spark plug wires, and it was fixed! Hopefully this will help.
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spark plug wires, rotor and cap, plugs, etc. are all new. i dont exactly have any hills here in delaware so how else would i check the injectors?
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More Turbo
Joined: Feb 2015
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From: NE Ohio
Did you double check that your wires are right after you put on the headers?
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More Turbo
Joined: Feb 2015
Posts: 508
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From: NE Ohio
I doubt timing could do that, even if its far off enough that the truck still runs. The plugs can tell you alot. A stuck injector will leave a plug black and smelling like fuel, or dead injector would be cleaner looking than the others. To rule out an injector issue pick up a stethoscope at the parts store for $10. Post pics of them if you can.
Cargo Master
Joined: Jun 2013
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From: Somewhere n North America
"ever since we put headers on my truck" here is the key......
Check the output signal of your O2. 0.1 - 1.0 vdc?
How far from the original location, did you install the O2?
Check the output signal of your O2. 0.1 - 1.0 vdc?
How far from the original location, did you install the O2?
Last edited by vjsimone; Mar 15, 2017 at 11:16 AM. Reason: Adding text
Lead Driver
Joined: May 2011
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Do the other things I suggested, check fuel pressure regulator and pressure, then unplug o2 to see if it is computer demanded fuel ...if the fuel pressure and regulator are good. Gotta rule out some easy stuff here.
Fleet Owner
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From: Kentucky