I bought my XJ in 2020 and put up with a intermittent cruise control. Until recently it has been useable but would disengage going over a bump. It would also disengage when the turn signal was used.
Now the cruise control accelerates when the set button is released OR the resume switch is used.After resetting the on/off switch if you use the resume slider sw the vehicle accelerates. The maint manual says that when turning the cruise sw back on cruise memory is dumped and the speed has to be reset using the set button. But after turning the cruise switch off you can push the resume switch and the vehicle accelerates until you hit the brake or turn the cruise switch off.
So today I changed the turnsignal/wiper/cruise stalk today thinking that the wiring was broken or frayed in the column.
After installing the new stalk it looks pretty but still acts in the same manner. I hate to fire the parts cannon at it but I could use some help
Any ideas on where I should start?
Thanks,
74Plb
90 Cherokee Limited

 

I wish I could help but I don't know anything about that cruise control I would start by looking at a wiring diagram to see if there is a control module .

 

The main components are the control module, speed control sensor and the servo.
I'm leaning towards the control module being bad. The cruise engages with either the push button or the resume switch.
The cruise is locked out below 35mph by the speed sensor. So I think that the speed sensor is probably ok.
Above 35mph the servo kicks in but rather than maintaining a set speed it accelerates until you kick the system off with the brake or the cruise sw is turned off.
There's a control module available for 35 bucks with free shipping. I may start firing the parts cannon with that.
Thx for the reply
74Plb

 

If it has a control module I would think that would be the problem , on newer cars it is in the computer that runs the engine that's why I said look at a wiring diagram.

 

Hitting bumps could be a brake/cruise switch maladjusted.

 

I'll take a look at the cruise/vacumn switch today. Sometimes when I hit a bump or the vehicle got jarred the cruise would drop off and not reengage until I shutdown and I restarted the XJ. That certainly could be the problem there. I'm thinking the issue with the turnsignal activation is resolved but I haven't looked into that yet as the cruise goes WOT when the set button is pushed
74Plb

 

Spent a couple hours with the vacumn system today. My vacumn canister or ball has 4 ports on it. Two with 3/8 hose and two with the hard brittle plastic line with rubber connectors.Initially we hooked up a vacumn pump to the main 3/8th fitting on the intake and pressurized it. With the vac pump running it showed 30 inches of pressure. As soon as the pump was turned off the pressure bled down to zero. Is there any type of internal check valve in the stock canister? We couldn't find any obvious leaks or broken lines.
The servo diaphram holds good pressure and the solenoids in the servo seem to be working ok.
I adjusted the cruise control module to rule it out and when I set the speed it no longer goes WOT with the set switch or the resume switch.
if I set 40mph it will hold it briefly then start surging between 35 and 40 mph. So I'm thinking I have a vac leak or leaks.
If I go with a different 2 port canister off of a later XJ can I install the 2 additional lines on tees?
74Plb

 

Found this JPEG from forum member CCKEN in 2016. I didn't realize that the vacumn reservoir was a split chamber.
I ordered a 91 Crown reservoir from Amazon along with some new 1/8th tubing. I'll see if I can dig up a 3/8th one way check valve for the nipple at the intake manifold.
74Plb

 

Yeah, the reservoir is split. Yes, there is a check valve for each side.

I have a spare for my '88. I hooked my Mityvac to the vacuum source line, connected my vacuum gauge to one of the "outlet" ports, closed the other and pumped away. Once I got a decent vacuum reading I vented the Mityvac. You can see the vacuum remained in the chamber. I then tested the other side. Same result. Vacuum didn't bleed off until I removed the gauge. Perhaps if left on long enough. On my '88, if I don't start if for a few days, I can hear the vent doors move to their last selected positions once the engine starts.

Here are the pics. You can see the Mityvac gauge (white dial) is zero while the vac gauge (black dial) reads around 7.5 psi (what a workout getting it to pump that high)



Same here. MV gauge zero, vac gauge around 8 psi



The single "ball" tank is the way the later models are configured so I cant see why it wouldn't work. Mounting holes may be different.

 

The tank I ordered is the football shape but looks like only two vac ports. I'm not sure if it has check valves or not. Looks like the same mounting points, but I'm going to relocate it below the coolant tank anyway.
Might not even be dual vacumn chambers ? Guess I'll see Monday if the part comes in.
Thanks for the reply
74Plb
Actually it only has one vacumn port My eyrs are playing tricks on me

 

Ebay 90 XJ cruise control servo fixed the WOT issue. I figured the problem was in the cruise control module as the diaphram held vacumn on the old servo. So it was a 50/50 shot at getting it right the first time. Guess I'll keep the old servo as a souvenir
New Crown vacumn reservoir, plumbing, check valve and a couple tees of a 93 XJ in the local yard did the trick. I'll mount the new reservoir below the Renix coolant pressure tank.
74Plb