'89 Laredo cruise/vacuum problems

[ziggy2000]

Hello from a new member! I recently purchased an '89 XJ Laredo in pretty decent shape (still gets 20mpg on the 4.0 L engine at 195,000 mi. ) I am slowly trying to sort out some small problems, the biggest of which is the cruise control. I strongly suspect a vacuum problem somewhere, but even with the FSM I'm having a hard time sorting it out. I'll try to describe the conditions as best I can. 4.0 L engine, AW-4 auto trans, NP231 transfer case.

First, the cruise just does not engage. I've tested the stalk switch and it's OK. Haven't got to the speed sensor or other components yet. But under the hood there are some funny things going on. The 4WD light was on all the time, and I traced it to the 4WD switch (under the coolant reservoir) and found that the vacuum line to the switch had vacuum at all times, not just with 4WD engaged. The switch itself is apparently OK, as the 4WD light goes out when I pull the vacuum hose off. That led me to suspect that a hose was misconnected somewhere. While poking around in the general area, I found a vacuum hose that was not connected to anything! Try as I might I cannot find a comprehensive vacuum diagram in the FSM to help me figure this out.

There is a bundle of five colored hoses (red/green/blue/yellow/white) that are under the coolant res. The blue one is unconnected, the white one goes to a y-connector that leads to the 4WD switch. Yellow & green connect to some steel lines heading underneath, I assume to the front axle disco. Red t's off to a rubber hose running between the manifold & the blimp up front. The white & yellow hoses are spliced together into yellow, then go to a 3-gang connector (blue/green/yellow) that heads off down the back side of the engine. The red hose bypasses the 3-gang connector, and connects to a separate red hose farther back. Looks like these all end up at the t-case where I can see the 4 colored hoses connecting. Clear as mud???

My main question is, what does the blue hose normally hook to that is currently not connected? Could this be part of the cruise control problem? AFAIK all 4WD functions are operating correctly, as well as heating-A/C stuff. And I'm not sure where to check for vacuum leaks on the cruise system. Any help that can be given will be greatly appreciated!!!

Thanks!

Marty

 

[ziggy2000]

Okay, so after some deeper digging in the FSM, I found that these hoses are indeed part of the front axle disconnect system, and apparently hooked up correctly - the "unconnected" blue hose has a check valve on it. Now I'm worried that there might be some mechanical problem causing the 4WD light to stay on. I know that the transfer case is not in 4WD all the time, but I now suspect that perhaps the front axle is not disconnecting for some reason - the 4WD light switch is actually vacuum controlled from the axle disconnect shift motor. The shift motor is quite loose in its mounting and can be rotated freely. Is this normal? Unfortunately I don't have a vacuum pump to test the shift motor as called out in the manual - is there some easy test to perform to see if the front axle is disconnecting or not - i.e. raising the axle, rotating the wheel, and observing the front driveshaft? Could the vacuum switch on the transfer case be misbehaving?

This is a little perplexing to me, because a leak is pretty much out (I think) because it is not the lack of vacuum when there should some, but rather the presence of vacuum when there should be none! Maybe I'm totally wrong, but that's how it seems to me...

Any help you can give to this newbie would be greatly appreciated!!! Thanks!!!

Marty

 

[forgiven]

Yes , jack the front wheels off of the ground and spin the right front wheel, if anything else turns, right front wheel or d-shaft, then the vacuum motor is engaged. I'm not sure about the vacuum motor freely spinning though.
On the other hand there should be a resevoir and motor for cruise control. I believe I've seen said elements near the firewall inboard of the brake booster near the firewall. Just a thought, have you checked the magnet on the d-shaft and it's pick-up?
Sorry I can't be of more help.

 

[ziggy2000]

Thanks for the reply!

Okay, I just confirmed it... the driveshaft turns when I spin either of the front wheels, so it looks like the axle shift motor needs to be replaced. Unless there's a possibility that the vacuum switch on the t-case is not operating correctly??? Haven't found a procedure for testing that yet.

As for cruise control, haven't dived totally into that yet. All the wiring up under the dash looks to be OK, but I haven't started doing all the voltage etc. tests called out in the manual. I'm assuming the vacuum is OK, since the heating-A/C and other vacuum-controlled things appear to be getting vacuum - anyway the lines all look good up around the battery etc. I was under the impression that the speed sensor was under the dash, coming off the speedo cable - didn't know there was a magnetic pickup on the driveshaft??? I know where all the major CC components are, just haven't been able to wring them all out!

Then there's the matter of the rear main oil seal...

 

[martin]

Ziggy,

I had the same problem on my 88 XJ, I took it to the dealer to fix it since I wanted to keep it stock instead of installing a aftermarket system.

It would of been cheaper to go with the aftermarket system installed, I found the place in the yellow pages under "cruise controls". You may want to have the local speedo shop install an aftermarket kit.

My problem was solved by the dealer mechanic wrapping EACH wire in the dash board harness and the cruise control wires out to the servo with electrical tape. then he wrapped the whole bundle in tape.

You can not tell it but you have an Electrical Magnetic Interference (EMI) problem and wrapping the wiring to restore the insulation solved it on my XJ.

Martin

 

[ziggy2000]

Thanks, Martin!

I had read your solution in another thread, and I'm really hoping I can get away without having to do that! Maybe the aftermarket thing is the way to go. I still have some testing to do with the components before I give up totally, but first I am going to have to deal with the axle disconnect problem. I'll let you know how it turns out!

Marty

 

[martin]

Ziggy,

I failed to mention I paid the dealer mechanic for 6 hours of labor and the new parts he installed. I got the last cruise control yellow box left in the supply system.

The mechanic put in 64 clock hours to fix the problem. The dealer had the XJ for 2 months.... June 4 to Aug 3, 2001. I speedo shop guy told me "we don't even try to fix those, we just install an aftermarket kit".

Martin

 

[89xj]

did you check the vacuum lines leading to the vacuum ball in the front bumper? not sure if this has to due with your 4w drive problem, but it could effect the cruise control. also check the vacuum ball for cracks.

 

[ziggy2000]

Man, that thing is a pain to get at! I can sort of see it behind the bumper there, but can't really give it a good inspection. Looks like I may have to take the whole bumper off to get a good look at it. Anyway the lines up to where they disappear behind the headlight look OK. I know there is vacuum to the rear port of the CC servo, because I can hear it hissing when I remove the connector. Since that is the line that goes up front to the ball, I'm sort of assuming the ball is OK for now and not bothering to dig it out just yet.

Marty

 

[89xj]

sometimes the lines leading to the ball are craked beneath the battery. to get to the ball, you need to take the bumper off. you should still to a vacuum test on the lines leading to the ball to eliminate the possibility of a craked line.

 

[JKooshTJ]

This may be a bit out of place but I can tell that all the vacuum lines are screwy in mine or cut. Is the line going to the vacuum ball in the front bumper red. Because if it is, mine's severed all the way and I haven't even seen the ball yet!

 

[JKooshTJ]

Just checked mine and there's no vacuum ball, and I don't see any vacuum lines running up front. Is this normal for an 88 XJ?

 

[Yucca-Man]

Just checked mine and there's no vacuum ball, and I don't see any vacuum lines running up front. Is this normal for an 88 XJ?

No. The shape changed over the years, but the vacuum bottle should have been under the front bumper on the (US) passengers side. The lines run under teh battery and are notorious for picking up leaks from that area, so some owners relocate it into the engine compartment especially after adding an aftermarket bumper. If your HVAC vents operate normally and you get air through the vents then you've got proper vacuum operation from somewhere...