OK, I need a Ford Genius here. I have a 1998 Expedition...I'm not a motorhead + I'm a chick so not sure of the engine size, but I do remember the AutoZone guys telling me to just remember it is the bigger engine.

I'm at around 198,000 miles, btw.

Sometime in early fall I started to have a rough rumble to the truck, almost like I was running over rumble strips on the roadway...but it wasn't in the tires, it's under the hood, if that makes sense. Sometimes when this occurred, the "OD Off" light on my shifter would flash.

I once had it plugged in at a garage and they told me everything from change transmission fluid and filter to slip malfunction (I think) to fuel pump...many options. I did nothing. No one could really figure anything out..

Over the winter I drove it without issue. And I drove a lot. I have a child being treated regularly at a hospital 1 hour away from me, and I have been driving there and back sometimes once, twice, three times a week and sometimes every single day for appointments since November. In the cold, horrible winter we had, it did not rumble, magically, but when it got warmer in April for a day or two it did rumble here and there, but has not picked up again like it was in the fall. Honestly, thought maybe something got gummed up that worked itself out in the long, frigid PA winter we had.

Two or three weeks ago I had a kind of bounce to the engine (I just pumped up the music and started to car-dance....might as well go with it!) as I drove home from the hospital. I was also losing power. Stopped in at AutoZone and had the check engine codes read (different machine than the OD OFF light required?) and there was a spark plug needed. Got that changed by Mr. Wonderful and no problems.

Until yesterday. Went to go out and run some errands and it was riding EXTREMELY rough. Stalled at second intersection I came to a stop at. That was awesome because it's on a hill with a scary amount of not-able-to-see-cars-coming 2-way stop sign. Made it through and continued on about 1/2 mile to a church where I could turn around. Stalled at the church too. Almost stalled when I came back to same stop sign, but was able to keep it idling by lightly keeping my foot on the gas while waiting my turn to cross the intersection. Big hill to climb coming up to my street...by big I mean steep incline...VERY little power coming up that incline, thought maybe I'd stall and float back down, honestly, but I made it.

There are no flashing lights happening, no CEL and no OD Off light doing anything.

Passed PA yearly inspection in late March, don't know if that's important or not.

So now it's parked in my garage, waiting for some insight from you kind people. I read on another thread about an intake manifold elbow...I'm going to have Mr. Wonderful check that out for me, but I need any thoughts and ideas you want to throw at me. He's awesome and pretty much a genius but motors are not his strongest point...he is, however, very capable once he researches what to do.

 

If AutoZone told you the bigger engine, you have the 5.4. Did you change 1 plug or all 8? What is the maintenance history as far as new plugs, trans fluid and filter change/flush, engine oil, etc.

I suggest you get Mr Wonderful to check for codes, write them down if any (I'm sure you have something), and report back with your findings.

 

Sounds like you've done some research here to find the elbow issue.

To John's point, get us more detail if possible. However, it will probably one of three things for the running rough issue...cop, spark plug or pcv elbow vacuum leak.

The flashing OD light is something else tied to your tranny and as noted, will probably need a different reader.

 

If it was a big vacuum leak, such as with the infamous broken elbow, then you would get a CEL with codes P0171 and P0174. But even that doesn't cause lack of power.

The lack of power tends to be the result of more than one cylinder misfiring or insufficient fuel flow. A fuel issue can be the result of a clogged fuel filter, a weak fuel pump, or a bad fuel pressure regulator.

This is important...do you notice if it only does it when you're under a 1/2 tank of fuel, or does it also do it with a full tank?

 

I have not driven the car since I posted, however, Mr. Wonderful has and the mechanic has. They say it wasn't happening every time. So far, it has not happened on a full tank because it has been on the same partial tank for weeks! It does seem to happen more when the stop is at an incline, which would slosh the gas around to different positions...what was your thought as pertains to gas level? Mechanic sent us to transmission shop who said we need a rebuild ($2900) which is too much to put into this vehicle. If I keep it I also need new tires, alignment, etc. so the amount to keep it shoots up to near $4,000...I can get something else for that. I have this nagging thought that we should try the fuel filter before we list it for sale...just in case....

Do Expeditions often make it to high mileage? I don't feel like I see a lot. If I keep it I'd like to keep going to 250k....thoughts appreciated. I've got a kid to run back and forth to a hospital an hour away and the trips are frequent, so I need to figure this out!!

By the way, transmission shop said, when asked, they didn't remember if any codes showed, we just need a new transmission...that doesn't sit well with me but I didn't talk to them directly. We didn't pick it up till about 5 days or so after it was done because my daughter was in the hospital. Mr. Wonderful thinks they weren't being odd about it.

 

The fuel pump is immersed in the fuel only when the tank is at half to full. The fuel acts as a heat sink for the pump. A failing fuel pump will act up first when the tank is below half because without the fuel absorbing the heat, the pump runs hotter and has a harder time keeping the fuel pressure high enough.

 

Thanks for the input here!
I didn't answer every question, I realized...we never replaced all plugs. Just this one recently and one a year or two ago. The older one made Mr. Wonderful cuss. A lot. Fluid was never changed because we were told that can sometimes make things worse. My brother came up and checked it a few days after my post and said the fluid was sweet and red, which also makes me think tranny shop (look at me with the lingo here) might be missing the mark...




I think we are going to try a few cheapie things tonight and if no luck, let her go on Craigslist tomorrow. Cleaning throttle something-or-other and new fuel filter.

We've been eyeing a few older Explorers with third row seats....we may go that route.