I Have a 1997 F150 with 5.4l engine and 60000 miles. I t runs fine untill I really kick it when I'm going between 50 and 65 mph. Then it acts like it is running on only 5 or 6 cylinders. Normal acceleration it is fine. Any ideas. I have a K&N filter and a superchip but it was doing this before.

 

Hey MrO
i had this problem about 8 months ago and it kept getting worse it felt like it was mis firing at any speeds above 50mph.
Well one day coming home from work on a friday night "i wanna gonna go to the dealer next day anyhow" the check engine light came on. Well it turned out the dealer said the spark plugs were fried and the wires were bad and the engine plugs were arching out.
Well i got a tune up and she was back to being a BeasT!!!!
Hope this helps
Moose!

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97 F150 Longbed V8 4.6
K&N air filter
K&N FIPK tech MOD & removed elbow silencer
Tires: Yokohama 265/75/16 Geolander AT+
Hyper white xenon bulbs
Bedliner and raven shell
6 disc cd changer
Oil & filter used

Gasoline used

My Truck

 

Moose man, are you running a chip too?

 

Could be transmission shudder. When was the last time you changed the tranny fluid?

 

I wondered about maybe a bad coil but she runs fine even at higher speeds. It is only when I floor it that it cuts out.

 

I haven't changed it yet but it still looks good and smells good.I'm planning on changing it as soon as the weather gets a little nicer.I can't imagine that it is the transmission.

 

If you don't follow the Ford rec's on changing the tranny fluid, the result is transmission shudder.

Do a search on "transmission shudder" in the transmission forum. Check the link below for a quick starting point.

https://www.f150online.com/f150board...ML/000146.html

Hope this helps.

P.S. It could still be the engine, but considering the symptoms you listed, it's sounding more and more like it's the tranny.

[This message has been edited by Dennis (edited 03-11-2001).]

 

I have a simular problem it seems at 50+ mph a bit of a miss occurs can't place why . Had it in and said it was caused by a heater hose leaking on a coil.
heres the diagnosis on work order
Checked out :no eec codes, pinpoi NT P.ON.O61 electrical.
They replaced, heater hose, wire assembly ignition Jan 01 . (there is a TBS on this)
But that did not solve the problem and I don't think it is a trans. issue either.
As stated one previous post here, it could be the coil, or spark plugs . Ive read on a lightning post the plugs seem to be a problem .

My ride 98 f150 sc 4x4 ,4.6, 16800 miles.

 

Had the same problem with my 89 4X4. Changed the plugs and upgraded my plug wires and now it runs like new again.

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2000 Harley/Davidson F-150
Lund Bug Deflector
Ventshades
Century "Cargo Cover"
K&N FIPK Gen II
Superchip is on it's way!!!
89 F-150 Lariat 4X4 for the "dirty work"!