# F350 V10 Spark plug and oxygen sensor change



## theguynextdoor (Sep 18, 2007)

I have a 2008 F350 with 118,000 miles on it. It been worked hard its whole life with plowing and towing. My fuel economy has gotten really bad in the last couple months, even worse than it used to be. I can barely get through one plow route on a tank of gas. I keep up on the regular maintenance with oil changes, air filters, etc. 

I was thinking about replacing the oxygen sensors and spark plugs. They are all original. It runs fine, other than the excessive fuel consumption, so should I bother with the spark plugs and the potential disaster that pulling broken plugs out creates? Anything else I should check for causing this poor fuel mileage?


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## dieselss (Jan 3, 2008)

Have you ever done a throttle body cleaning or a fuel system cleaning?


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## PPP (Jan 5, 2005)

The website ford truck enthusiasts has a lot of good info on this. I have the 2005 version of this truck. Not sure how long your route is. These are tough on gas. If the check engine light isn't on. Plugs are not all that bad. There are plenty of tools and write ups on this. I had mine done for me.


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## Cornerstone PM (Jan 27, 2016)

A dirty mass air flow sensor will make you use gas. At 118,000 if its never been cleaned its over do. Make sure you only use MAF cleaner. carb cleaner will hurt it.


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## Whiffyspark (Dec 23, 2009)

PPP;2108650 said:


> The website ford truck enthusiasts has a lot of good info on this. I have the 2005 version of this truck. Not sure how long your route is. These are tough on gas. If the check engine light isn't on. Plugs are not all that bad. There are plenty of tools and write ups on this. I had mine done for me.


Not true. 118,000 miles I would do them. I'll see if I can post a graph later to show you.

I use an electric impact to do them. I have the lisle kit when they break. I think we charged $350 and an hour for each broken one


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## Plowtoy (Dec 15, 2001)

Did plugs on the 03 back in June? Piece of cake, just be sure to make sure its cold. Ive heard of guys using impacts, but I never have. I work on the 2 valve V10s all day in the E-series and have yet to break one, or take out the threads. I have had them blow out, and even one I just threaded back in and almost has 200k on it now. As for the 02 sensors, not sure id mess with them unless the lights on. I did them in one of our vans and even though I could see them with the dog house off, I still had to pull the Y pipe to change them.


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## Whiffyspark (Dec 23, 2009)

3 valves are the issue not two valves. Two valves are easy just the occasional blowout


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## tar (May 13, 2004)

Not meaning to hijack but is my 03 v10 a 2 valve or 3 valve


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## Plowtoy (Dec 15, 2001)

tar;2109663 said:


> Not meaning to hijack but is my 03 v10 a 2 valve or 3 valve


Should be a 2


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## theguynextdoor (Sep 18, 2007)

I ordered all new spark plugs and oxygen sensors. I pulled one spark plug out before ordering parts to see what kind of shape they were in. Came out and went back in with no problems. 

I'll post on the results of my fuel mileage once I change out the parts.


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## theguynextdoor (Sep 18, 2007)

I changed all 4 oxygen sensors, fuel filter and 10 spark plugs. All the spark plugs came out easily without breaking. The truck is now getting 1.5-2 mpg better since I did the work. It wasn't running rough or poorly before, but it's definitely running smooth now.


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## oldmankent (Mar 2, 2001)

That's good to know. I thought when you changed the plugs getting the engine good and hot was better for removing plugs.


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## theguynextdoor (Sep 18, 2007)

oldmankent;2130469 said:


> That's good to know. I thought when you changed the plugs getting the engine good and hot was better for removing plugs.


I did these after the truck had sat in the garage for almost 2 days. I always thought a warm engine was better for removing spark plugs, but I read otherwise online. I put a shot of penetrating oil down in the threads before I took them out. I also spent a lot of time blowing the spark plugs holes out before I removed them so debris that was around the boot didn't fall into the cylinder.

I was getting around 7 - 7.5 average MPG before doing the work, and now its back up to 9.5-10, which is a huge difference when mileage is that low. It's also been warmer outside, so I'm sure that helps a little. I also have 4.10 gears so the trucks barely breaks 10 on the highway.


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## Whiffyspark (Dec 23, 2009)

It's varying school of thought. Honestly I don't think it makes much of a difference what you do. Doing them by hand seems to be what causes them to break, I'm guessing because it isn't exactly square when you pull on the ratchet usually. 

Last time I did them I unbolted the coils and then let it run for a while. Shut it off and hit all of them with an impact. Didn't break any


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## Too Stroked (Jan 1, 2010)

Whiffyspark;2130592 said:


> It's varying school of thought. Honestly I don't think it makes much of a difference what you do. Doing them by hand seems to be what causes them to break, I'm guessing because it isn't exactly square when you pull on the ratchet usually.
> 
> Last time I did them I unbolted the coils and then let it run for a while. Shut it off and hit all of them with an impact. Didn't break any


Most of the guys I know who work at Ford dealerships are using 3/8" cordless impact guns to remove the problematic (2004 - 2008 3 valve motor) spark plugs. There were numerous "suggested" methods of pulling them out. Some said warm motors, some said hot. Some said to use Penetrating Oil while some said to use Carb Cleaner.

It appears that a 3/8" gun has just the right amount of force (torque) to break them loose and shake them out slowly. Using a gun with more torque can cause just as many problems as trying to ease them out by hand. Other helpful hints include applying Nickel Anti-Seize to the shank - _not the threads _- before installing the new plugs and using a torque wrench to seat the new plugs properly.

For all of the hype around how bad it originally was to get these plugs out, the better Mechanics have found ways to make it go pretty uneventfully now. And if you do break a plug, the Lisle Tool makes getting it out pretty painless.


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## Whiffyspark (Dec 23, 2009)

I don't soak them I just take them out. I don't think it makes a difference. I had to finish one a guy filled up the entire spark plug holes with pb blaster. Everyone of them broke off and he walked away from it lol


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## theguynextdoor (Sep 18, 2007)

I used this spark plug socket, which has a wobble extension built into it so it stays straight on the plug, even when the ratchet it not. $12 at advanced auto.
I also put nickle anti seize on the plugs when I put the new ones in.


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## Too Stroked (Jan 1, 2010)

Whiffyspark;2130832 said:


> I don't soak them I just take them out. I don't think it makes a difference. I had to finish one a guy filled up the entire spark plug holes with pb blaster. Everyone of them broke off and he walked away from it lol


I agree. The problem with putting _anything _down the bore in an attempt to soak the threads is that the liquid always ends up in the combustion chamber, then the crankcase. Then if you don't change the oil ...


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## Whiffyspark (Dec 23, 2009)

theguynextdoor;2130836 said:


> I used this spark plug socket, which has a wobble extension built into it so it stays straight on the plug, even when the ratchet it not. $12 at advanced auto.
> I also put nickle anti seize on the plugs when I put the new ones in.


I have those. I think they're part of the problem when you do it by hand. Snapon makes a plug socket that is deep as the cylinder with no swivel. Always meant to buy one but never did.


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## Too Stroked (Jan 1, 2010)

Whiffyspark;2130869 said:


> I have those. I think they're part of the problem when you do it by hand. Snapon makes a plug socket that is deep as the cylinder with no swivel. Always meant to buy one but never did.


Once you use it, you'll wonder how you ever lived without it.


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## Whiffyspark (Dec 23, 2009)

I got out of it and went back to working for myself. Nothing like having $50,000 in tools in your personal garage to fix your 4 year olds toys lol

I'd like to do side work but it's hard to find. The only thing I do is lighting installs on trash trucks now. I worked in a shop before I left that worked on everything from smart cars to class 8. So I've had a lot of experience


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