Missing under load/heavy acceleration.
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Missing under load/heavy acceleration.
Hi everyone I have a 98 F150 with the 4.6 and I’m out of ideas what could be wrong with my truck. It all started a few weeks ago when I ran it low on gas. It started sputtering then got a lil better then got to where it is now. When I floor it it accelerates but misses, I can feel the loss of power and when it shifts up it starts missing worse than it does it higher rpms. I’ve replaced both coils, the iac valve. Cleaned throttle body and cleaned out the egr passages that was completely blocked with carbon. Checked my fuel filter and I could blow through the inlet side very easy so I don’t suspect this. The only thing I haven’t checked is the plugs themselves. The wires feel new and the guy I bought it from a month ago said they had just been done. Also haven’t pulled the fuel pump. Would it be possible for the pump to “half fail” causing my problems? Any help would be appreciated. Thank you
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Joined: Dec 2015
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From: Utah
Chances are it is a bad plug or wires. I have had a bad set of wires, right out of the box. Took the car to a dealer because it had new wires, plugs, etc. but it still missed. All the dealer did was swap to Motorcraft wires - problem solved.
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So maybe it’s just a coincidence my problem started after I ran close to empty on gas?
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From: Utah
Well, your terminology you used was that it is "missing". That would have nothing to do with the fuel level.
You could always check the fuel pressure and make sure you are around 37 to 41 psi (ish) with the vacuum unplugged. But I stick with my original assessment if you say it is missing.
You could always check the fuel pressure and make sure you are around 37 to 41 psi (ish) with the vacuum unplugged. But I stick with my original assessment if you say it is missing.
Thread Starter
Junior Member
Joined: May 2018
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Well, your terminology you used was that it is "missing". That would have nothing to do with the fuel level.
You could always check the fuel pressure and make sure you are around 37 to 41 psi (ish) with the vacuum unplugged. But I stick with my original assessment if you say it is missing.
You could always check the fuel pressure and make sure you are around 37 to 41 psi (ish) with the vacuum unplugged. But I stick with my original assessment if you say it is missing.
Senior Member
Joined: Dec 2015
Posts: 23,191
Likes: 8,622
From: Utah
I am pretty sure Autozone rents a FP gauge. Start there, the you'll know for sure. If the pressure is low, change the filter first.
But if it is missing, I'm not sure how a fuel pump is going to cause a cylinder to miss.... the whole truck would run like crap on all cylinders.
But if it is missing, I'm not sure how a fuel pump is going to cause a cylinder to miss.... the whole truck would run like crap on all cylinders.