HELP: What's causing this miss?
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Tuned
Joined: Feb 2003
Posts: 426
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HELP: What's causing this miss?
I'm hoping somebody who has experienced the symptoms I'm getting on my truck can give me some hints as to what the problem is.
Three days ago my truck ('87 F250, 300, fuel-injected) began missing badly when I'm lightly accelerating, a little over idle. It is idling great and it accelerates well. When it begins to miss, I can accelerate and there is no miss. No bad codes are showing up. The plugs, wires, distributer cap are all fine. I can find no vacuum leaks. I did find a dead spot on the throttle position sensor and replaced it, but the miss is the same. I had an extra ignition module, so I put it in. Again, it made no difference. Fuel supply seems to be okay.
I need the truck for hauling building materials to a job a couple of hundred miles away (I'm pulling a trailer) and am supposed to go back there in five days. I hate to start off in it with it running like this.
Can somebody help me out here? Thanks.
Three days ago my truck ('87 F250, 300, fuel-injected) began missing badly when I'm lightly accelerating, a little over idle. It is idling great and it accelerates well. When it begins to miss, I can accelerate and there is no miss. No bad codes are showing up. The plugs, wires, distributer cap are all fine. I can find no vacuum leaks. I did find a dead spot on the throttle position sensor and replaced it, but the miss is the same. I had an extra ignition module, so I put it in. Again, it made no difference. Fuel supply seems to be okay.
I need the truck for hauling building materials to a job a couple of hundred miles away (I'm pulling a trailer) and am supposed to go back there in five days. I hate to start off in it with it running like this.
Can somebody help me out here? Thanks.
Junior User
Joined: Dec 2008
Posts: 51
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have you determined if it's an electrical miss or just running rough just above idle? it sounds like fuel, not electrical. like fire240 said, fuel filter first. i then would look to the fuel pump if needed. i can't imagine an accelerator pump intermittent. they either work or not in my experience. but, i've been wrong before...
Junior User
Joined: Mar 2009
Posts: 51
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i had the same problem with my 89 f150 300ci efi after replacing the fuel filter,cap,rotor,plugs and wires it still didnt fix it it turns out it was my catylatic converter i just punched a bunch of holes in it and it fixed it just fine now but i also live in a county where there a re no emissions tests so i can get away with it
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Tuned
Joined: Feb 2003
Posts: 426
Likes: 4
Thanks for all your suggestions. Turns out it was the gasket on the egr valve. Why this didn't show up as a code, I don't know, especially when I checked the voltage strraight off the oxygen sensor and it showed a very lean-run condition. But the problem is over.
Texas_rebel21-- Do you mean you punched the holes through the internal core material on the cat? Or through the sides of the cat?
Texas_rebel21-- Do you mean you punched the holes through the internal core material on the cat? Or through the sides of the cat?
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