I just recently started driving my 2004 D2 on longer distance drives (NC to Delaware & NJ & back) so I'm new to using cruise control on the beast. Is it normal for this vehicle to constantly hunt for the power to hold a set speed on a nice flat stretch of highway? It does gradually, like as in several minutes, damper out somewhat but it cycles between heavy acceleration and coasting/deceleration for quite a while after setting/resuming a speed or after a change (uphill or downhill) that affects the speed. It's almost enough to make me airsick and I'm a pilot! Is there any way to tweak the system to calm it down or at least make more frequent/less aggressive changes? I think the slack in the cables is about right...what else should I check?

 

Put the slack on the cables at 1-2MM on both cables. Anything larger like 4-5MM = Cruise Control is going to surge. It makes a big difference in acceleration feel (no more dead pedal feel or laggy response), and the CC will not surge nearly as bad. I never really noticed the surging on a 4.0L V8 D2, but the 4.6L can certainly surge. They had several tweaks for it back in the day, but it never took the surge out totally.

 

A VERY well known failure point is the vacuum hose between the vacuum pump and the actuator of the cruise control assembly.

In many cases, a leak causes the system to not work at all. I suppose it's possible that a small leak could inhibit the performance of the cruise control but not render it completely inoperative.

Remove the hose and inspect it, and if you see any cracks replace it.

Heck, A replacement length of tubing from any auto parts store probably doesn't cost more than a couple of dollars, so just go ahead and replace it and see what happens.

Please report back.

 

And of course I have the 4.6... I'd have to measure it but I'm quite sure it's more than 2 mm slack--probably closer to 5-6. I might as well replace the vacuum line for that too, while I'm out there chasing the SAI demons. Good to know it's fairly common on the 4.6; if I can at least get it tamed a bit, I'll know it's just a quirk. Fascinating how much vacuum-run stuff there is on these cars. Reminiscent of dad's old '51 ****** with it's vacuum powered windshield wipers!

I'll let you know what I find out. Probably be a week or two before I get to it.

 

Usually if it was vacuum related the CC would never engage or it would engage and quickly stop unless the leak is tiny. Surging CC on a 4.6L was very common, and some people tried older 4.0L Hella CC modules, but from all the D2's with 4.6L's I've seen cable tension is #1. 1-2MM of slack and it should make a big difference.

The CC on my 99 with a 4.0L = engages and never surges. It just downshifts the second I roll over an overpass due to 188HP pushing 32.5inch tires, 4 roof rack mounted 9inch LED lights, and an ARB bumper with an Extreme Hi-Lift mounted to it. I'm as aerodynamic as a box car.

 

good to know about the hose. Mine stopped working last year after doing the turn on, work for a bit, and then shut off.

 

The other part which can get a pinhole or leak is the actual rubber bladder/bellow as it constantly moves in/out when in use.

 

Nothing to add about the cruise control, be we make the same drive from NC to DE all the time. Not many people in DE, I probably know you...thats where I grew up. :-)

 

Follow-up... I adjusted both the throttle and the cruise control cable cams (throttle cable per the RAVE manual spec and cruise control per Best 4X4's advice). Cruise still hunts a little but much better than it was. The gap on the throttle cam was about three times what the RAVE manual shows and the cruise control cam vs throttle cam gap was about twice what the RAVE manual shows, which was even worse compared to Best 4X4's suggested. It's tolerable now. Of interest was the cable locations were switched from the arrangement in the RAVE manual.
Still a weak system compared to pretty much any other car I've owned. Of course if I drove it off road more, like I should, I wouldn't even need the CC!

Thanks Best 4X4!

PS humroot--believe it or not, I make the drive for work--I'm an airline guy based at Newark, but I'd much rather sit & wait on reserve in Delaware than Jersey. I was based at Dover for a couple years with the AF, though: 2009-2011.

 

No problem