2005 f150 with 4.6l. So as the title says, I am having an issue in 4 low. I need to use half throttle or more to get any kind of response when I am in 4 low. When I am in 4 hi or 2wd I have instant throttle. Do any of you have any ideas on where to start troubleshooting? I know I have to replace the actuators... P.O. ran it with severed vacuum hoses, but, that shouldn't cause the issue I am having should it?

 

So what kind of response are you getting at half throttle?

 

Something to try: Run it in 4LOW with the Overdrive Off; see if the response changes.

 

basically nothing happens. If I put it into 1st, it's a little better, but still not great.

 

Sounds to me like the transfer case is messing up. Check the transfer case shift motor to be sure it is traveling the full distance to fully engage low range.

 

Okay I'm not there to see for myself so I have to ask, are you sure it's a lack of throttle response or are you maybe just not realizing how little the truck moves in low until you catch the higher gears?

 

yep, its lack of response. Its like the engine doesn't come off idle until I hit about half throttle . My wife's truck is an '05 also, except it's a 5,4l and no issues with the 4wd. I'm scratching my head over this, it doesn't seem to affect anything, but it bugs the hell outta me that i don't know what is causing the issue. I do have more pressing problems with the truck that i need to address, so I may throw it on the backburner for now.

 

When 4L is selected, the transfer case motor circuit sends a signal to the Computer.
This changes the normal programmed RPM and road speed shift schedule so it matches the LOW gear ratio change for all gears it tries to shift to.
If not, the engine RPM would be too high to shift at the proper signaled shift points.
This truck uses electronic throttle control.
There may be some issue with the 4L signal to the computer.
Check for transmission codes 836 through 839, 1729, 1781, 1804 thru 1877 etc. or any code involving the transmission.
If nothing is found, it becomes a case for a good tech with a Ford dealer Scanner or a high end instrument to diagnose the system, with the capability those tools have.
When electronic throttle is involved it can get even more complicated.
Good luck.

 

well dammit... figures it wouldn't be something simple. Gonna get the exhaust fixed ( mainly because it is literally hanging by bailing wire), then the 4wd vacuum system, then it will be time to look at the 4lo. Thanks guys for your responses, I will post back when anything else crops up.