Lurching Cruise Control - Any Ideas?

[Longs]

When I use cruise control on my '93, there is a jerky, lurchy feel, especially for the first 5-10 miles of use. It seems to smooth out, or at least I must get used to it, the longer I use it. I don't lose speed, then pick up to the set speed, then lose it again, it's more like a very quick stabbing at the throttle. When it's more noticeable, I can see very minor fluctuations in the tach. I don't get this when the cruise is applying the accelerator steadily, like when I'm climbing a grade, it's mostly on fairly level roads where the cruise is just maintaining the set speed. It's almost like the car is cutting out when the cruise is engaged. When I'm not using cruise, everything is fine and the truck doesn't have any signs of surging or cutting out.

The other day it was dark when I was using cruise, and I swear that I saw the ABS light flicker when the cruise surged, even though I wasn't touching the brakes. I then started watching and never saw it again.

I've looked for a vacuum leak, and I haven't found any obvious signs yet. I also don't see any signs of transmission fluid in the vacuum lines, although I haven't checked the modulator at the transmission.

Has anyone else experienced anything like this? Are there any sensors or connections or relays specific to the cruise control that might be causing it?

Thanks,
Longs

 

[TPLYNCH]

It could be the speed sensor going bad.....

 

[Longs]

Where is the speed sensor? Is it the same sensor that's on the transfer case to prevent engaging 4WD at too high a speed? Would it be likely to affect any other systems besides cruise? Any idea how much it costs?

thanks

 

[Longs]

Now I've seen some postings about a speed sensor for ABS mounted on the rear differential - is this the same sensor that controls the cruise control on a 4WD? I did see my ABS light flash when the cruise was acting up, even though I wasn't using the brakes...

 

[TPLYNCH]

I think the same sensor is used for all functions, but I'm not sure about where it is.... Sorry.

P.S. Kurts not the champ any more. What?

 

[Longs]

Two Sensors

I might be wrong about this, but y understanding of the 1st generation Explorers, which I own, is that the ABS to each front wheel is independent, and the rear wheels share a common sensor. In addition to that sensor, there is a speed sensor on the 4WD transfer case. I believe that the primary function of that sensor is to prevent engaging the 4WD above 55 mph. You can drive above 55 in 4WD, but the sensor keeps you from initiating 4WD at high speeds. I suppose that with the later versions of 4WD, this may not be necessary.

P.S. - Although Angle rules, Stone Cold will likely retain in the three-way title match, unless they give it RVD. What?! Unless they give it to RVD.

 

[Alto]

Similar problem with mine as I was going to the Tranny shop. The Guy at the shop downloaded the code. He said that the code read "Incorrect gearing at 4th gear" He said that was the reason it was surging!
Maybe a different problem!
Hope yours is not the same! Mine turned out to be a Rebuild.