98' AWD 5.0, Funky Vibration/Pulsation

[Ford_Racing_Guy]

Ok i've recently bought a 1998 AWD 5.0 XLT

its in great shape, only as 81,000 on it, i've only had it since tuesday and it does something odd that i've never encountered,

while accelerating moderately to full throttle there is a vibration in the gas pedal and sometimes it actually pulsates, kinda like the brake pedal does when the abs kicks in, there is also an addition noise that corresponds with engine RPM, more like some kind of vibrational rattle at certain higher RPMs, i ran a search and couldn't find anything.



Any ideas? i haven't poked around under the hood yet but i figured i ask to see if anyone has encountered this problem and could point me in the right direction.

Comments Much appreciated.

 

[Ford_Racing_Guy]

no ideas?

 

[MountaineerGreen]

I havent had that kind of problem, wish I could help. Maybe someone will jump in here and help.

 

[410Fortune]

This is very odd, the gas pedal is only connected to the throttle body with a cable, the cruise control cable is piggy backed to the throttle cable at the throttle body.

My point is this is a simple you push the pedal and it pulls the cable which opens the throttle body butterfly. So its a mechanical system

Now the Gen II Explorer (yours) has been known to have issues with the rivets that hold the gas pedal bracket to the firewall, I would start by looking at the pedal assembly under the dash and its connection to the firewall, make sure its not loose.

Then I would remove the cruise control cable from the throttle cable (at the throttle body) and drive it, see if the issue remains.

The pedal should not pulse at all, ever.

I would check those two things, then inspec the cable itself.

Does the entire truck vibrate? A broken engine mount or trans mount may allow the engine to move around enough to effect your cable?

Just thinking out loud here.

 

[Ford_Racing_Guy]

thanks for the comments, i'll have to take a look at the pedal more closely


as for the vibration/noise, i looked under the hood when i got home this morning (i work second shift) and it appears that a bracket on the left side of the engine bay is rubbing on the firewall when the engine twists, so i imagine that i might be able to grind part of that bracket off as long as it doesn't harm anything.

as for the pulsation i have no idea, sometimes it does it, other times not, i took a look at the linkage and whoever owned it previously had it zip-tied to the hood latch cable, looked like it was pull over at a funny angle so i cut the tie and straighten the cable out more so it looked better, for now i unhooked the battery to reset the ecm and tomorrow i'm plan on seafoaming it just to see if does anything

and perhaps i will try the cruise control cable deal


thanks for the help

 

['97 V8]

take a picture of said bracket before you cut or grind.

 

[Ford_Racing_Guy]

well i think i made progress today, i was poking around under the hood and i decided to unhook the Speed Control Module.

i thought that did it cause it didn't pulsate funny all day until once on the way home, seems to do it when i come to a stop and then accelerate over some bumps.

i may go ahead and disconnect the speed control linkage as well and see what happns, i'm gonna hook the plug back up and see if it does it more or not.

this is very confusing to me.