Cruise Control (ASCD)

[asavage]

So, in the FSM, Nissan calls the Cruise Control the "Automatic Speed Control Device", how 'bout that?

The '82 Owner's Manual says, (I think, from memory) that the CC will not operate above 76 MPH, and a few years ago, when I was driving through Nevada where one can actually use a CC at those speeds, I found that the manual was correct. If set while above 76 MPH, it will set to 76 MPH only.

Checking a handy 1983 Owner's Manual, it says 78 MPH is the magic number. Same for the '84 OM.

The CC will drop out if the vehicle speed drops 6 to 11 MPH below setpoint. Scared the bejesus out of me: I was on CC, and gaining serious elevation in Nevada's high desert (on my way to Caliente, NV ?), CD cranked up, black smoke pouring out behind me, not another car for 20 miles, when suddenly the engine like, dies. Oh, no!

After the panic attack, it was only the CC dropping out. Apparenty, I'd found a grade at that altitude that the 80HP LD28 couldn't hold 65 on.

===============

BTW, there's a typo on the ASCD schematic (pg EL-139 in 1982, EL-151 in 1983). There's a spurious ground connection point listed to the right of the "Inhibitor Relay (A/T)" wire to the "Stop Switch". Cross-checking with the ASCD wiring diagram a few pages on (as opposed to the wiring schematic), no such ground point is shown, and it's a dead short circuit if it was actually there.

The 1984 FSM (pg EL-138) has that ground point eliminated, so I guess they figured it out eventually

The 1981 FSM (pg EL-128) does not show that ground point either, but then again it also doesn't show a clutch switch. Apparently, in '81 there was no clutch switch for the ASCD!

[danridley]

Trivial, but amusing: the CC won't set below a certain speed -- 30ish, I think -- but if you set it high, you can coast it downward to about 15 before it shuts off. Useful for the long stretches of empty 25mph roads around Blaine (WA).

[asavage]

Trivial, but amusing: the CC won't set below a certain speed -- 30ish, I think -- but if you set it high, you can coast it downward to about 15 before it shuts off. Useful for the long stretches of empty 25mph roads around Blaine (WA).

I remembered about the 30 -- this is pretty common -- but the annoying thing that I think I recall is that once you drop below whatever, it forgets the setpoint, and Resume doens't work anymore. I think.

[kassim503]

my cruise control on my gas maxima has a few problems. if i engage it at 60+ mph itll the engine would go to wide open throttle and wont back off no matter how fast you go. and at the other speeds it would engage but slow down by about 3 mph. also if you set it at 59-60 mph it would make the engine start surging and disengage itself. can anybody figure out whats wrong all the lines are connected but im not too sure if they are leak free

[asavage]

I don't have a clue on this one. Obviously the servo is working, and the switchgear is not involved. Offhand I'd be suspecting the speed sensor, then the control module, in that order. I don't have spares of either, unfortunately.

You've got an '83 gasser, right? Take a minute to put that info in your signature block (click on "Profile" at the top of any page), and I won't be guessing Guess I'll go take my own advice now!

I'll stare at the FSM on the ASCD tonight and see if anything comes to mind. That's an odd symptom. Usually the switches go bad.

(I had the CC servo cable snap 400 miles north of LA last week, on my old Aerostar. Spent Christmas Eve morning at a Pick-A-Part in El Monte! Took Dad with me, he hadn't been in a JY in years, and think he really enjoyed it! $4 for us to get in, $6 for the cable.)

[asavage]

Well, I've looked at the system diagram. 1983 FSM, pg EL-159. The speed sensor is a make/break switch in the speedo head itself.

If it was mine . . . I guess I'd connect up the ocsilloscope to those leads (B & BY), jack up the back end and run it up to 65 indicated, watch the pulses and see if they're linearly changing. But that's because that's the equipment and background I have.

If you can get the parts cheap enough, get a speedo head and ASCD Controller (left kick panel, lower). Swap the Controller first, because it's easier. Then swap in the whole speedo head or instrument cluster, whichever you find easiest. If the latter fixes it, you can try swapping out the sensor only, though I can't tell if it's easily serviceable separately or not. I've done this kind of work before, and it can take a steady hand.

I don't have a spare ASCD Controller or speedo head, but I could pull the Controller out of my driver and loan it to you -- but I want it back! You pay shipping both ways, and I'd want it back within, say, two weeks. Mine works fine (it's an '82, but I think that won't pose a problem).

[later: Parts Catalog says the same Controller part No. is used for all diesels; speed sensor not available separate from the speedo assy.]

But I really think it's the speed sensor, from your description.

[kassim503]

sorry for all the trouble, i figured out the problem, one of the lines had a little slit in it, so i just changed out the whole line and its running great now. thanks for the info though

[asavage]

A line to what? Dump valve? Servo?

[diesel-man]

Without even looking at it there are some little vacuum lines on the firewall be the auto dipstick tube, by the fuel filter, and coming off of the vacuum pump on the alternator that get hard, crack, leak vacuum. Didn't read this post over well enough and subconsciously? assumed that it was already checked. Easy enough to overlook.
Wayne

Al:
I will have to go and check which Fast Glow boxes are good and be sure (again) which is bad. need time.....

[asavage]

I would think that leaking vacuum line(s) would create an entirely different symptom. I'd sure like to know which line was bad in this case.

[kassim503]

Never followed up on the cruise control hose that was slit, it was a small vac line that run from the intake manifold to some cylindrical thing. The cruise control still dosent like to be used, symptoms only died for a few weeks. Dosent bother me too much because there is too much stop and go traffic on long island for cruise control to be used. The VSS is probably broken.