I bought a 98 Expedition Eddie Bauer 5.4 2WD a couple of weeks ago, and I've inherited some issues. Apparently the guy that sold it so me thought it had 142k on it. But it turns out that it's got more than that. The odometer is stuck at 142285 but there's an oil change sticker from nearly 3 years ago that says 278k. I have no idea really how many are on it, but surprisingly the interior and exterior are in excellent shape. So I'm willing to work on the problems to end up with a really great truck.

The major issues that I'm having now are a short in the flasher circuit (blows the fuse as soon as you push a new one in), an A/C compressor that doesn't come on when I'm adding freon, and a engine that seems to go into limp mode after about the first 2 miles of the day. The first time I take off, it'll suck you into the seat. After then, it misses pretty bad from 30 to 50 and when getting up to speed, it's really sluggish like I'm towing 10,000 pounds behind me. When going over 55, it runs much smoother but still doesn't have the pep when getting on the throttle. It drinks gas too but that may just be the change from a 1.8 Mitsubishi motor I had to the big 5.4.

A couple of days after I got it, I changed all the plugs to Motorcraft plugs, changed the air filter and the intake tube (all chewed up and leaking at the TB). Both the old plugs and air filter looked well used but nothing out of the ordinary. The COPs looked nearly new. The only Check Engine codes I'm getting are the Upstream passenger o2 sensor slow to respond.

I've got a manual on its way. And I'd rather not start throwing expensive parts at it unless I can be fairly sure they're necessary. I do have this wire that's not connected to anything. It's coming from the mass of wires heading into the PCM. Could that be what the o2 sensor should be connected to?

 

For the performance issue I suggest that you check all of your vacuum connections and elbows and use a vacuum gage, if you have one or can borrow one. The engine should have about 20-22 inches of vacuum at an idle. If you take a vacuum reading and post it here with a pic if the needle jumps around. There are several persons here with a lot of knowlege that will help you interpret the gage reading. A vacuum gage will let you know if the engine is sound as well as if there is a problem with timing or valves or whatever.

 

I'll have to look into getting a vacuum gauge. From what I'm reading it's a good thing to have around.

Today I had it running and disconnected each coil connector one at a time to see if it changed the idle and all the ones I could reach (the front six) all showed good. So unless the bad coil(s) just happened to be the back two, I'm kinda wondering if it's the fuel filter. That would kinda explain the off-and-on nature of the miss and the general lack of power; if I hit the gas at 40mph it just sputters and very slowly gains speed. Not knowing the maintenance of the truck, I kinda have to assume that the factory fuel filter is still in it after probably 300K miles. That's a lot to ask of the factory filter.

 

There is a vacuum connection at the rear of the intake manifold. It is a 90* elbow that often comes apart in the center of the bend and causes the problem you describe. It is very difficult to reach but it is reachable.
Check out this thread; [url]https://www.ford-trucks.com/forums/1184239-2003-navigator-bank-1-sensor-1-replacement.html[/url]

 

Changed the fuel filter and ran half a can of Seafoam through the brake booster line. Still not as much pep as I'd like, but it runs a LOT better. (Lots of white smoke though.) Will have to see if it stays good tomorrow. Getting hit with rain bands from Isaac now.

 

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Took this video of the vacuum gauge hooked up. You can also hear the tap-tap-tap-tap-tap-tap-tap since this was on the driver's side of the engine.

 

It looks like you are a little low on vacuum, Mine holds steady at 23 inches. On the good side, yours is not jumping around as bad valves or rings would indicate.
Have you checked ALL of your vacuum lines and connections?

 

That vacuum reading appears to show that the cat or cats are clogged.

 

Yeah I'm gonna be taking off the TB for cleaning tomorrow and I'm gonna go over the vacuum hoses and elbow while I'm in there. I'll do another reading afterward to see if it improves.

 

This guy must be a troll! All of his posts are the same dribble.

 

OK..... After 8 hours of blood sweat and tears, I'm pretty much still where I was. Took off the throttle body and took it all apart. Cleaned out the awfulest mess of carbon crud I've ever seen. Put everything back together with new gaskets when needed. The vacuum gauge still shows the same reading as before, but now the engine seems more sluggish than before and doesn't want to pep up until 3k RPM.

Tried to change the PCV elbow (You were right Moto Mel, had a hole in it on the very bottom.) but the one that the parts stores show as for a 98 5.4 doesn't fit mine. The one on my engine has a much bigger tube on the intake side and there was just no stretching it enough to cram it on there. The guy at Advance was stumped because his computer showed the same one (that doesn't fit) for every year (I don't believe my engine is the original one and am not sure what year my engine is). Even the spark plug wire boot fix I saw somewhere wouldn't have worked because the biggest boot the parts guy could find wasn't near big enough. So as a last ditch effort I put some adhesive sealer (gas and oil safe) on the crack in the old elbow, wrapped the whole thing in a couple of layers of black tape, put it back on and hoped for the best. Doesn't look like it worked so I'm thinking I'm gonna have to head to the stealership to try and match one up.

I also found another cracked hose. The top one off the throttle body to the EVAP stuff above the brake booster. Actually looked like it was melted where it pushed against the EGR valve. I cut away the bad section and joined the ends with a gutted ink pen and routed it away from the EGR valve.

Probably gonna be a couple of weeks until I can work on it some more, so I'll give an update then.

 

As I was reading your post I was going to suggest the "spark plug boot fix" but you beat me to it. If you have to do it, you might consider using a copper pipe elbow, the solder type you find at most hardware stores. Like those used in HVAC or small plumbing jobs and some heater hose to put it all together. It won't be perfect but might get the job done until you get the correct part(s).

 

OK, did some more work on it today. Took the TB off again to get to the PCV elbow. The people at NAPA couldn't find an elbow to fit it since mine had a 3/4" fitting on the back of the intake instead of the usual 5/8". Ended up going to the dealer and contributing to their child support payment in exchange for the whole PCV assembly, even though it didn't match my setup at all. What I had on the truck was a PCV valve that joined directly to a plastic tube that went straight back and made a curve to go behind the intake and then had an elbow that connected to the intake.

Apparently I have a 99+ engine since mine has an aluminum intake instead of the plastic ones I've seen. It also was supposed to have a "heated PCV system" with one tube going to the back of the intake and another branching off and going to the TB. The previous owners (or maybe the previous owners' mechanic) had made a non-heated setup work by plugging the TB hose and using a spark plug boot to connect it to the intake. So now I at least have the right part that seals correctly. And it has MAJOR suction when I put my finger under the PCV valve.

While I was at NAPA I picked up some thick fuel hose that the lady said could be used as a vacuum hose to replace the one from the TB to the EVAP controller. Works great, if not too great since it was a VERY tight fit on both ends. And after having to remove and reinstall the TB a second time to get the gasket right (Engine started but would die immediately), the truck idles about the same and has the same vacuum reading; but drives about as good as I can really expect it to. The throttle response is a little lagging but doesn't miss anymore on the road like it did before. I swear I can hear a hissing sound though, but when I shake all the vacuum hoses I get no change in the sound. So maybe it's the alternator or the fan (which I hope to convert to electric later on). Right now I'm pretty much satisfied with how the engine is running.

 

I have been working on my 02 Exp. on and off for a year now when I have the time. I haven't found the cause of my problem yet.... A little back ground info.... 2002 Expedition E.B. 5.4 engine with about 235,000 miles. I have checked the vacuum lines, replaced the EGR, Crank Sensor, Fuel Pump, Fuel Filter, ALL COPs, Plugs, and I will have to check but I believe I replaced the IAC as well... Here' s what its doing... Just driving out the road under a load or not the truck will Jerk Very Hard sometimes it continues to jerk lightly and then it will pick back up again. Sometimes when it Jerks it will completely shut off. I can turn the key off and back on and it starts right back up again. The Fuel Milage is TERRIBLE too!!!!!! like 6 and 7 pulling a small trailer and 9 and 10 at best on the high way. Any suggestions that I should try??? I haven't put a vacuum tester on it, I just looked at the lines. The one thing I will do this weekend is get a vacuum tester though and see what it shows. I would like to get it fixed the truck is in great shape besides what ever is causing this Jerking...
Thanks!
Jason