Hi all. Let me first say that this is my first post. Like a lot of others, I have been a reader of forums, but never joined one until today. I felt compelled to write a post about my experience that I hope may help someone else. I have a 2000 Excursion V10 with 195k miles. I started having a misfire about 6 months ago. First code was for #10, then it cleared on its own after a couple days. Then 2 months later, #8 threw a code, and then cleared out its own. Then a month ago, started getting multiple misfires. Started with 2 & 8 and ran poorly, shaking at idle and no power. So I figured it was time for new coils and plugs, since it had been 70k since they were changed (40k on new injectors). So I changed them and cleared the codes. No difference, but now the misfire is on 3, 6, & 8. So I did everything that everyone suggests, like checking the connections at the plugs, looking for worn or damaged wires, swapping plugs, swapping coil packs, and swapping injectors. Misfires never followed any pattern. Now I have 3, 6, 8, and bank 1 too lean. I cleaned the MAF, ohmed the TPS, and cleaned the IAC (what a tough location).still nothing. It's been several tanks of gas, Lucas fuel treatment, new fuel filter, checked fuel pressure, checked vacuum leaks, opened up steering column to check for rubbed wires, everything. So I am pulling my hair out because in this forum and several others, the only things left were major problems, like compression (head gasket, rings, etc), but I had decent pressure 138-150psi). Now the codes are 2, 5, & 9. So I decided to go back to basics. I started with the air supply. As I moved to the throttle body, I almost stopped. From the outside, It looked pretty good. But I pulled it off and was freaked out by what I saw. I can't post pictures, but it was terrible. A coating of black tar, 1/8" thick in some places. So after a half day of cleaning the TB and the spacer between the TB and intake, I put her back together. I decided to do the new Seafoam intake spray clean, as well (i did 2 cans). She is like a new truck, no codes (going on 159 miles now). I know that some of you will be compelled to disagree with me, to tell me that there is no way that a dirty TB could cause a misfire code, blah, blah. I know. Good intentioned people on forums said the same. Even a Ford mechanic I spoke to couldn't tell me where to go next. But maybe there's a guy out there that really needs to hear this because he needs his rig to get to work and support his family. This is for you. And maybe you can return the favor and share your experience on a forum, so I can benefit from it.

 

Wow, that's a lot of troubleshooting.
That's great the fix was actually not that bad, just finding it.
When there are random misfires it's usually something from the intake forward to the air filter or from the fuel rail back to the tank or power or the controller (PCM), things that affect all cylinders.
I know you found the problem, but did you check the crank position sensor, the camshaft position sensor, or engine coolant temp sensor/thermostat?
Could you see any of the throttle body sludge by just looking down inside or did you have to remove it?
Had you ever run fuel injector/throttle body cleaner thru the fuel before?

 

When I had 4 misfires at the same time on my truck when I first bought it, I changed all the plugs and boots as well as the COPs of the 4 offending cylinders and that cured the misfires. I still had the dreaded P0171 and P0174 combo which turned out to be the PVC hose under the throttle body. All of these fixes and problems are very common on V10 engines.

 

Yes, it was a ton of troubleshooting, especially for a guy who is not a mechanic. Like I said, I just felt compelled to share my experience because I just could not find it discussed where I looked. I know the info may have been out there, but I never read anyone's thread discussing the possibility of multie misfires being linked to a nasty throttle body. Honestly, if I hadn't done it myself, I may not have believed it either.

 

And yes, I use Lucas fuel treatment every third fill up. I had never used the Seafoam spray, just run it straight into a vacuum port or other opening. I would recommend it because I think that the atomizing spray would work better than pouring it in.

 

Interesting story. The only thing I can think of that would do that is if the throttle body in these vehicles is not completely closed at idle, and the computer expects some amount of air to get past. With the IAC at max open, maybe there wasn't enough air getting through.

I don't think you said in your first post, but were these misfires felt when on the highway or accelerating? If not, those misfires were at idle, and the throttle body being that dirty can definitely be the cause.

Great find

 

The power problem with the stumbling and shaking was most prevalent between idle and 1800 rpm. Basically during normal street driving. Acceleration was poor. Highway driving was ok, but any attempt to accelerate or downshift was poor. That's why I still don't quite get why the TB helped so much. At idle and low RPM, I can understand the misfire as the truck is looking for the right mix. But at freeway speed and higher RPM, I would think it would clear up. Maybe the seafoam loosened up some sticky valves? Or maybe cleaning the spacer between the TB and intake had something to do with it. Perhaps there was a partial clog in one of the orifices, like the PCV? Anyways, hope it helps somebody.

 

Good read.

So you DID take pictures before cleaning? There's gotta be a way you can share. Upload them to your gallery? I'd like to see what it was like.

 

Believe ot or not, this was AFTER cleaning it up some...
Here is the spacer between the TB and intake
Figured it out...here they are, although I'm a little embarrassed that these were on my rig...

 

Holy crap, that's dirty

 

Inspires me to do a TB cleaning.

 

What kind of oil has been run in this engine?

 

Severe blow by?

 

That's what I first thought, too, but how would it get to the throttle body plates?
Doesn't the PCV dump into the engine after the throttle body?

 

The valve cover opposite the PCV valve is plumbed into the intake tubing before the throttle body. So if there's a LOT of blow-by, it'll wind up passing through the valve body.

On the other hand, maybe the PCV system wasn't working for a long time.