Hello all and hoping someone can help. I have a 1997 F-150 XLT 4X4 EXT Cab 4.6L Automatic O/D. 110,000 miles.Great truck. While driving the truck at 50 to 60 mph, at 1500 RPM, the truck has been surging. The RPM goes from 1500 to 2000 back and forth. The tranny does not seem to be gearing up or down,(shifting out of O/D ). Just the RPM. One day it will be fine the next it will surge. I do all recommended maintainance. My tranny fluide is where it is to be. Has anyone had this problem and what could it be? confused: Thanks in advance. Dave.

 

vacuum leak?

 

Thanks for the reply. If it is a vacuum leak, should the check engine light not come on? I have no warn lights on. Some people say the injectors need cleaning, ABS breaks is another, change Tranny fluid, and now a vacuum leak. Has this ever happened to anyone else? If it has then they will know how they corrected the problem. I hate when things happen to me that has never happened to others. You would think that I could win the lotto.Thanks all. Dave.

 

Hello to all. Still have not fixed my problem yet. I got so mad I just took the truck and floored it. Drove the **** out of it for a good 2 mins. Now it seems to run great. It's been two days now. Did some more research and came up with some more possibilities. The throttle position sensor or Mass airflow sensor. What do you think? Thanks Dave.

 

Whens the last time you changed the fuel filter?

 

The fuel filter was changed 45,000 miles ago.

 

My truck revs up in or out of gear, and i usually have to shut it off or wait for it to go back to normal, i was told it could b a "Mechanicaly sensitive Leak"

Ex.: the gasket behing your TB or you mite want to try pulling the IAC valvle and clean it and lube it

 

45k is a long time on a fuel filter - change it on general principles.

 

It is only happens when I am actually driving the truck. Starts and idles fine.

 

Does it try to speed up at all when it surges up, or just stay at a steady speed? Perhaps seem to fall on its face when it surges maybe too?

 

The speed stays constant, does not accelerate speed wise when rpm goes up. It is like driving at 55mph, keep rpm at 1500, shift into nuetral, then step on the gas pedal till the rpm goes up another 400 to 500 rpm totalling 2100 rpm. It will stay there for 3 to 5 seconds and then go back down to 1500 rpm.It will do this my hole drive.

 

Talk to Ford mechanic. He said drive the truck on the highway 55 miles mph while the foot is still on the accelerator just touch the brake pedal until the brake lights come on. If your rpm goes up 400 rpm than it is your torque convertor. That is exactly what my truck is doing. So for any of you that have the same problem it is your torque convertor. Til next time Dave.

 

um... that is normal.^^^

 

I posted a similar problem about a week ago just mine does this while at approx 30mph and jumps about 1500RPM. I was going to bring it up when I go for my first oil change. I spoke with the service manager at my shop who used to work in a transmission shop and he said its most likely the torque converter. Anyone know if there is a reflash for this problem? This doesn’t sound normal so if anyone finds the cause or solution please post it.

 

your situation isnt normal, but driving in overdrive and tapping the brake, will unlock the converter.