Sluggish 4.6L at about 40mph?

cschroth1 · #1 (**permalink**) 02-14-2004, 10:09 PM

Hi,
I just bought a 1997 f-150 4x4 stepside extended cab pick-up.
It has 72,000 miles and auto transmission.
I notice sometimes around 40mph it like shakes and struggles?
If I hit the gas it changes gears,and has plenty of pick-up.
The truck has been tuned up,checked out by a dealer,and transmission shop.They say all is fine.
Otherwise it runs great,and has plenty of power?Any ideas?Thanks

BrianA · #2 (**permalink**) 02-14-2004, 10:57 PM

Howdy and welcome to FTE! Hope we can help you figure out the problem.
When the transmission shop checked it out, did they change the fluid? My dad's F150 did the same thing at about the same mileage. His was a '97 as well. Changing the transmssion fluid solved the problem.
Maybe other guys will have more ideas.
Let us know what was wrong if you get it figured out.
Again, welcome to FTE!

LxMan1 · #3 (**permalink**) 02-15-2004, 01:02 AM

Could be torque convertor chatter, or a weak spark plug or bad wire. They will show their weakness the most at those speeds with the converter locked.
Jimmy

sucktin · #4 (**permalink**) 02-18-2004, 10:33 AM

These engines aren't known for their low-end torque, so when you lock the torque converter at a low speed and give it a little bit of gas (not enough to make it kick out of OD), they can be sluggish. I try to keep the thing out of OD unless I am doing over 45...I think it puts less stress on the converter from going in and out of lock. Changing the fluid id a good idea though.

hood · #5 (**permalink**) 02-20-2004, 02:37 AM

cschroth1:
Does it feel like you are driving over railroad tracks when you say it "shakes"? Then does it vanish after you hit more speed...45-50mph?

If so, its torque converter shutter. Fluid change may help if the converter isn't shot.

-hooD

Keith1984 · #6 (**permalink**) 03-01-2004, 11:51 AM

Around 40 is when it drops to OD. It's ok on on nice flat lands but when you hit a hill it is annoying.

fireball69 · #7 (**permalink**) 03-02-2004, 09:38 PM

Mine started doing it at about 70K miles. Replaced plugs (2nd set) and wires. Helped out. I used to say it was the "little engine that wanted to prove it could do it". Kept trying to go instead of downshifting. Recommend new plugs and wires, and checking air and fuel filters. The engine could just need a little more air or fuel to climb.

Keith1984 · #8 (**permalink**) 03-02-2004, 09:48 PM

Doesn't a partialy plugged exhaust cause similar issues? I saw a set of plug wires for $133. These things got solid gold wires or something? Wires for my car were like $40, granted it was a V6 but I don't see two more wires being another $93.

fireball69 · #9 (**permalink**) 03-03-2004, 06:30 PM

A partially plugged exhaust could to. More likely fuel/air filter or sparks. The 100K miles on one set of plugs is bull. Normally last only 36K under most mixed driving. If only drive on highway I guess 100K is possible. As for plug wires, they 8.5 mm. Probably a lot bigger than you car's wires. I got my last set at NAPA for around $85.00. Look around you can find some deals.

Bowzer · #10 (**permalink**) 03-03-2004, 09:34 PM

My 1996 crown vic. did the same thing @165 Kms. I changed the fluid and filters .Now runs great. It really used to shudder under load before.