Hello,
I/we have owed this old 97 2X short bed 4.6L V8 w/97kmi ( since new and it's been a really reliable old truck. Yesterday I had a unusual and scarey thing happen in my driveway. I was parking a trailer and loaded near limits. The drive is on a non trivial slope. I was trying to pull the trailer up and forward but the left rear tire was slipping on the old asphalt and weeds. I was managing tire spin and getting a little creep with no smoke and slight noise. Then in an instant, R_O_A_R I was at very high power with blue smoke billowing from the fender in about 2 seconds. I shut down. That was a big WTF Over. When I restarted the engine shot up past 4k RPM and I shut down. This repeated 2 more times. After many minutes of walking around and having my wife search the net for possible help i tried again and all was NORMAL. The truck seems to be working just fine, cruise works, there are no issues with any throttle settings.

I am looking for someone who understands that old cruise system and want to know if my conjecture is reasonable for this event. I had been cruising on the highway previously at 50mph with cruise control. I had not manually pressed the Off button and likely just disengaged cruise with the brake. I suspect that while I was spinning my tire to get a little more traction to pull forward a foot the RPM went up to the point the truck was above 25mph and then managed to bump the RESUME button while looking over my shoulder. That is just a wild **** guess. Then the cruise said Yes Sir and I got wheel spin that looked like the Sunday drags at the line. The cruise stayed clamped on the throttle cable through a few restarts so at ignition the RPM surged. And somewhere in that I must have done something to disengage the throttle.

I find no svc bulletins or other reports of this kind of event and the truck is as near as I can test working fine today.

Is this really serious or should I just go on using the machine? It would be bad if it happened in stop-and-go traffic on the freeway.
Thanks

 

I am not an expert, but this is my thoughts on the issue.

Per the owners manual:
If you turned the ignition off, the CC memory is deleted. As such the CC will not/can not resume a specified speed.

I would be more concerned with the possibility that there is a problem with the throttle linkage or throttle body.

 

Replace your throttle cable.

 

Shutting the motor down kills power to the CC and memory.
Speed is set from the speed sensor not the throttle opening.
Restarting means the wheels /speed sensing is not active for this to happen on it's own.
Why not take a look at the hardware your foot moves to effect the same action. It could be the cable from the CC servo has developed a fault.
A gas motor is a variable efficiency machine that runs on air control with a little fuel injected to expand the air as opposed to a diesel that normally has no air control, runs wide open, but controls power by controlling fuel only.
Good luck.

 

Thanks all. I will continue to troubleshoot this problem. I am bothered by the part where the power increased under what seemed like a CC command. It may be the throttle cable but I don't understand how that could cause the power to increase and then not repeat or at least seem sticky or sluggish. It is very smooth and fast responding at this time.

Unfortunately, my service manuals are 350 miles away at home. I'll make another post after some more testing and possible work. Going to a shop without a clear repeatable problem is big no-no for me. My options include disabling the CC and drive home carefully.

 

If you believe that the speed control module actuated in your driveway, the safest way to prevent any future occurrence would simply be to disconnect the servo cable from the TB and unplug the module's connector.


Is it possible that a floor mat slipped and engaged the pedal?

 

FYI, if you disconnect the cruise module electrically, you'll lose the horn, Also, I have taken cruise modules apart and found rusty gears, so it can get sticky inside there.