Ford Expedition with slow acceleration, strong vibrations, and gas smell

My 1998 Ford Expedition XLT with V8 5.4L engine has been having issues for about six months. It first started off with a strong gasoline and burnt rubber smell coming from the front of the car within a few minutes of starting the engine. Later, the whole car began vibrating and would intensely shudder every once in a while when idling. The car doesn’t accelerate well from a standstill.
The RPM will climb up to 3000-4000 while going from 0 MPH to 10 MPH, then it will lurch forward a bit and it pick up a little more speed. It struggles again around 15 MPH until it hit 20 MPH when it will lurch again and pick up normal acceleration. Once I try to go 40 MPH or more, the whole will start shuddering loudly and still struggles with maintaining speed. I have not attempted to drive over 50 MPH. The best acceleration I can get is when I take 30-45 seconds to slowly press the gas pedal and work my way up to the speed I want.
I was also following my father in another car while he drove the Expedition and on the highway, I saw sparks come out from the back of the Expedition’s undercarriage when it climbed up an overpass.
When driving over roads that aren’t smooth, or when I accelerate, there is a sound from the back of the car like jangling chains or metal rods. It still makes the sound while the gas pedal isn’t pressed or the gear is in neutral, so I think there is something, but have not seen anything underneath that could jangle around. While looking underneath, I saw that that some areas looked rusty, but not cracked. There is also a black piece under the engine that looked like it was made of plastic. It looked wet and oily and had a 2-3 inch opening in the center. I feel that there was supposed to be some sort of cover there.
I now only drive it when it’s unavoidable, usually once a week or less, and usually distances of 5 miles or less.
I think the problem is with the use of fuel in the engine (fuel gauge fluctuates all the time, especially while driving on hills).
Thank you in advance for any advice and help.

With those symptoms, I would find it hard to believe that the Check Engine Light isn’t lit up, or–possibly–even flashing, despite the fact that you didn’t mention anything about the CEL.

Is the CEL lit up?
If so, you need to have the stored trouble codes read (gratis) at an auto parts retailer.
If the CEL is flashing, you need to have the vehicle towed to a mechanic, a.s.a.p.

If the CEL is not lit up, please verify that the CEL is actually working when you turn the key to start the engine.

The fuel gauge fluctuations are probably unrelated to the main symptoms. Good idea to have the battery and charging system tested though.

Beyond that, your best bet, with all these weird symptoms, is to take it to a shop for an inspection and diagnosis. If I had to make a guess I’d say one of your problems is a leak in the exhaust system. Modern engines don’t run well unless the entire system from the intake air box all the way to the tailpipe is air tight.

If you smell raw fuel…you more than likely need injector o rings… sounds like they are leaking. They have an O ring for the fuel rail…and an O ring where they enter the intake manifold…both can fail and if they both fail…you will have leaking gasoline, strong smell in the car, and it can inhale unmetered air at the manifold. ALL things you do not want. Not to mention the loss of fuel rail pressure which would affect the three other injectors on that bank.

All of this needs to be looked at Post Haste…forget about driving it unless you enjoy engine fires. They can be fun I suppose, but Im not partial.

Blackbird

The Check Engine Light is on. But since I can’t afford to have it repaired and this is the only available vehicle I can use since my own car was wrecked, I need a specific reason to convince the owner (my father) to take it to a mechanic. That’s why the car has been like this for 6 months.

“The Check Engine Light is on…I need a specific reason to convince the owner (my father) to take it to a mechanic”

That is why I suggested earlier that you take it to an auto parts retailer (Auto Zone, Advance Auto, O’Reilly, possibly Napa) where they will “read” the stored trouble codes free of charge. Perhaps showing your father the trouble code (or, more likely, multiple trouble codes) will convince him to repair the car. It will not repair itself, unfortunately…

Nobody could possibly give you a correct diagnosis from afar without knowing the stored trouble codes, and finding out what they are–gratis–is the best way to start the process. Come back here with the specific codes (the format will be similar to “P0123”), and we can try to give you further guidance.

I need a specific reason to convince the owner (my father) to take it to a mechanic.

How does “Fully Engulfed Devastating Vehicle Fire” sound as a reason to get it fixed ?

Blackbird

‘How does “Fully Engulfed Devastating Vehicle Fire” sound as a reason to get it fixed ?’

That would certainly convince me, but (no disrespect intended), I think that the OP has as much of a father problem as she has a vehicle problem.

Ekeoma wrote:
But since I can’t afford to have it repaired and this is the only available vehicle I can use since my own car was wrecked, I need a specific reason to convince the owner (my father) to take it to a mechanic.

I’m almost at a loss for words here. The symptoms you describe in your original post would cause any sensible person to bring the car to the shop immediately.

I hate to say this, but in this situation I’d consider sabotaging the car in some minor way so that it doesn’t run at all or so that it runs so poorly that there’s no choice but for your father to bring it in for diagnosis. I wonder if there’s something you could do easily to get the car into limp mode so that it doesn’t have to be towed but so that it can’t really be used. I bet the regulars here would have some good ideas on that.

Pull a few Coil over plug terminals…run her on 6 cyl…and it will get repaired.

Fire you dont want…trust me

‘‘Can’t afford to fix it’’ ?
Excuse my White A** . .BUT . .
( in no uncertain terms )
YOU CAN’T AFFORD - - NOT - - TO FIX IT !

Just that fuel smell ALONE is the red flag !