Truck looses power and shifts rough

5

Asked by Jan 30, 2017 at 11:34 AM about the 1994 Ford F-150 XLT 4WD LB

Question type: Maintenance & Repair

Ok guys. I've got a 1994 F-150 4x4 with an Automatic Trans and push button 4x4 controls.
History:
I got this truck from an older woman who had it just sitting in the woods for a year or two. Brought it home for inspection. Replaced all brake lines, calipers, rotors, cylinders, brake pads and shoes.
Lights - only 1 head light worked, out of all the lights.
Tracked down many wiring problems... removed a small grocery sack of extra wiring for trailer lights and what ever... all addition wiring not necessary was removed. All factory wire repaired to the best of my ability (and I'm fairly good with my wiring).
Wiring harness hanging out of the back of the transfer case was all chewed up by forest critters. Made all apparent repairs there with the exception of a possible ground wire (bare silver braided wire) Don't have a clue where it came from so I don't know where to attach the new one.

Problem:
When I take the truck out and drive it with the 4x4 turned OFF, it seems to lose power. Foot on the floor but only getting 20-30 or even 40 mph... BUT no power.
Then suddenly, power will KICK in with a forceful thump and the truck takes off like it's race day !
While driving it will suddenly start knocking, like it's trying to shift into 4 wheel drive. Indicator light by the 4 x 4 button is glowing slightly red, but it's NOT on. Light glows bright red when the button is pushed on.

When I drive the truck four wheel drive mode it acts perfectly normal. NO knocking... NO lose of power... NO issues.

So I'm wondering, given that the indicator light for the 4x4 seems to always glow slightly red while driving with the 4x4 in OFF position, if that ground cable underneath has something to do with this poor driving issue ?

Could there be something else that I missed ?
O2 sensor need cleaning ?
Other sensors ?
I'm thinking that even if the sensors need cleaning, based on the fact that it drives just fine while the 4x4 is ON, that this whole issue is based around the transfer case.

Any help please...
Old GM Guy !

8 Answers

109,715

First, check for codes, it makes life a little easier on everyone. Ok if nothing comes back there are several things that can cause you to bog down. such as the TFI module, did you change the fuel filter, check the fuel pump pressure, i think it should be at about 42 to 45 PSI, You may want to check the timing

5

Thank you sir, but did you read my entire post ? Truck drives absolutely great while in 4x4 mode. Just great ! No problems... plenty of power... no issues whatsoever. Drives as it should. :) It's only when I take it out of 4x4 that it does this.

5

I might add too, I do not have the ability to read codes... I'm not that advanced yet in my little shop.

109,715

Opps, yes try cleaning the sensor

1 of 1 people found this helpful.
5

Thanks Cometguy61. Also, I did replace the fuel filter in my initial work-over prior to driving the truck.

5

Thanks AskTrannyMan. I really would like to solve the issue and avoid the "work around". I live in the extreme northern parts of Minnesota... in the woods, so I have a "real" need to be able to utilize this four wheel drive vehicle. Could the issue be stemming from that Misc. Ground wire I found hanging down there ? I found the wire attached to the frame rail, but in the neighborhood of the transfer case. Could the missing ground link cause the indicator light to glow slightly even when in the off position ? Is the transfer case supposed to be grounded to the frame ?

5

AskTrannyMan, Thanks.

5

Mr. AskTrannyMan, I read your comment, re-read it again two more times and compared your recommendation with some information that I gathered reading other peoples issues elsewhere on this forum. Thank you sir. Between your comment and a couple others I was able to find the problem... I'm pretty sure anyway. I took that slave motor off the back of the TrXfr case and noted as you described. I also noted that my wiring was not up to par... I am so ashamed (I pride myself on my wiring work), but I had a loose connection. I had used ordinary butt connectors & shrink tube the first time, but they were not all tight. I removed the loose butt connectors and soldered the wires. No chance of them becoming loose now. Shrink tube of course to seal them from the elements. Test drove the truck a mere 5 miles and it seemed to run fine. Will take it to town tomorrow and put some gas in the tank for a second and more thorough test drive... 40 miles there and back. Thanks again... Have a great day sir. The image is what the transfer case wiring looked like when I brought it home.

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