2007 Expedition - Surging/Bucking while Driving - No Codes - No Misfires

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J Tuck

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I've got a 2007 Ford Expedition (Limited 4X4) that I've been having trouble with for a while now. It bucks/surges while accelerating, and while cruising at highways speeds (any and all loads). It seems to run fine right after starting up after sitting overnight, but once I've been driving awhile (5-20 minutes), the bucking begins, and usually continues until I get to where I'm going.

This all started February of 2021, when I swapped my tires to a (stock size) mud/snow tire for winter. This is when I first noticed the bucking during acceleration only. But it was infrequent and only during acceleration. I swapped back to my summer tires (again, stock size) and never noticed the truck bucking all summer while I was driving it. It's now nearing winter, I've swapped back to my winter tires, and the bucking/surging is back.

So far, I've tackled the easy items. Drain and filter for transmission... New (one piece Motor raft) spark plus... New air filter and MAF sensor... And problem is still happening in a big way.

I've checked my fuel pressure at idle (parked) and it shows ~70 psi, both at idle and pre-cranking. I have a fuel filter I am about to change, but that doesn't seem like the right fix. Going to change it anyways. Couldn't hurt, right?

As the title states, the Mode 6 data shows 0 misfires every time I have checked, and I have no codes showing up from any of the modules... Until a few days ago... When I started up the truck on the first below freezing morning of the season, I started it up, and let it warm up (more than usual) before heading out for the day. When I got in it, it had the wrench icon on the dash... So I plugged in my reader, and pulled codes...

I got:
U0073 (Pending)
P1500 (Grey)
U0073 (Grey)
U0100 (Grey)
U0101 (Grey)
U1900 (Grey)

I've looked all those up, and it looks like a bunch of stuff stopped communicating briefly, and threw a code for Vehicle Speed Sensor Intermittent.

I'm lost, and all the upcoming potential fixes look like they'll be $250-$500 for parts, each... Any ideas?

- Desperate and Going Broke
 
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J Tuck

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Just a little more information:
Truck has 193,000 miles. I believe most of it's parts to be original (was owned and maintained by a local fire department, I'm second owner).

When I start from a light and floor the accelerator, it will buck all the way from start until about 5000 RPM in second gear, and once it hits 5K, it smooths out, gains power, and goes through the gears perfectly... even after shifting from 2nd gear and goes below 5K. But again, once I get up to speed (45 - 65mph), it will surge all the way down the road again.
 

Trainmaster

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I know what you write about misfires, but it sure sounds like one. When were the plugs last changed? Any aftermarket cheap coils on the truck? You might enjoy pulling one plug and looking at it. If this was my truck, I'd pull the difficult one in the back, as that may NEVER have been changed. An awesome job, but I'd force myself to do it, as to me this sounds ignition related.

Check and clean the throttle body.

Check your battery cables and grounds, plugs into the computer and those basics in case this is electrical related, as that shower of codes may indicate a loose connection somewhere.

Lastly, I'd check fuel pressure, as low pressure could cause this sort of thing though usually not on low throttle acceleration. I'd also look around for vacuum leaks, check the PCV valve though all those would probably show a code.

I'm no expert, but that's what I'd consider.

Folks here have mentioned clogged converters with miss symptoms. I never had that experience but I believe you can check them with an infrared thermometer. You may want to research that a little.
 

B-McD

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You mention the tire swap as the trigger/cure - I'd be thinking some sort of ABS sensor or speed sensor perhaps? Since I have little true mechanical skills, I would disconnect the battery with the winter tires on, plug it back in and see if it can "re-learn" with the new tires on. Just a thought and pretty simple to help eliminate stuff. Good luck! Must be maddening to not know what the culprit is.
 
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J Tuck

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I know what you write about misfires, but it sure sounds like one. When were the plugs last changed? Any aftermarket cheap coils on the truck? You might enjoy pulling one plug and looking at it. If this was my truck, I'd pull the difficult one in the back, as that may NEVER have been changed. An awesome job, but I'd force myself to do it, as to me this sounds ignition related.

Check and clean the throttle body.

Check your battery cables and grounds, plugs into the computer and those basics in case this is electrical related, as that shower of codes may indicate a loose connection somewhere.

Lastly, I'd check fuel pressure, as low pressure could cause this sort of thing though usually not on low throttle acceleration. I'd also look around for vacuum leaks, check the PCV valve though all those would probably show a code.

I'm no expert, but that's what I'd consider.

Folks here have mentioned clogged converters with miss symptoms. I never had that experience but I believe you can check them with an infrared thermometer. You may want to research that a little.
I changed the plugs maybe 1000 miles ago now. We changed all 8 myself. Trans Flush was about 500 miles ago now. MAF about 250 miles ago. I will certainly go through all my connectors and check grounds. Good things to try... That's what I'm looking for.

Is did check fuel pressure and it's running ~70 psi at key-on and idle. Also, it does appear to have original 2007 coil packs on all 8 cylinders. Boots didn't look cracked or anything when we changed the plugs. I will look at your other suggestions after I go through the grounds.
 

Trainmaster

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Was it doing this before you changed the plugs? Any difference after replacing them? Are the wire connectors on the coils falling apart? Sometimes the harness plugs break and they don't lock onto the coils well.
 
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J Tuck

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You mention the tire swap as the trigger/cure - I'd be thinking some sort of ABS sensor or speed sensor perhaps? Since I have little true mechanical skills, I would disconnect the battery with the winter tires on, plug it back in and see if it can "re-learn" with the new tires on. Just a thought and pretty simple to help eliminate stuff. Good luck! Must be maddening to not know what the culprit is.
I will give the disconnect and drain the capacitors in the computers a try (re-learn). That's a no cost solution I haven't tried yet.
 
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J Tuck

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Was it doing this before you changed the plugs? Any difference after replacing them? Are the wire connectors on the coils falling apart? Sometimes the harness plugs break and they don't lock onto the coils well.
Yes, was doing the bucking before changing the plugs, too. No difference after changing. Bucked on the second drive after changing. Wasn't doing it everyday at that point though. It's everyday now.
Edit: Coil Pack plugs are in good condition and clip in securely.
 

Josha907

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Pretty tall tale sign of a bad coil. Really feel it at like 45 when it just locks in overdrive. light throttle that's when you'll feel it really bad.
 
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